bacterial | fungal
| parasitic | allergic
| autoimmune | neoplastic
| endocrine-related | miscellaneous
Introduction: Skin problems in dogs are among the top reasons for a visit
to a veterinary clinic. This discussion will review many of the most common skin
problems seen in dogs. The information will be divided into infectious, allergic
and autoimmune (immune-system related), neoplastic (cancerous), endocrine (skin
problems caused by problems with the organs that excrete hormones and related
substances), and miscellaneous skin diseases (scaly skin, pigment abnormalities,
nutritional skin diseases, etc.).
Infectious Skin Disease
Bacterial Skin Infections:
Introduction: Bacterial skin infections are commonly grouped
under the term "pyoderma," meaning a skin disease that causes pus.
Pyoderma is further broken down into more specific categories. The bacteria most
often responsible for pyoderma is Staphylococcus intermedius. There is
almost always an underlying reason for the presence of a bacterial skin
infection in dogs; however, this underlying primary cause is not always found.
- Superficial pyoderma: Bacterial skin infections are considered to
be superficial when they are in the outermost layer of skin (the epidermis)
and the hair follicles. Any irritation to the skin can lead to a superficial
bacterial skin infection. Common irritants of the skin include fleas, mange
mites, dermatophytes ("ringworm"), and other external parasites.
Chemicals or toxins, which may be found in common household items such as
hairspray or houseplants, can also cause irritation. These bacterial
infections can also occur anytime the skin is abnormally dry or oily.
Superficial skin infections may suddenly appear as painful, red ulcerations
which ooze clear to cloudy discharge (acute moist dermatitis or "hot
spots") or may progress more gradually as patches of hair loss,
redness, and scale (dandruff).
- Deep pyoderma: Any bacterial infection which involves the lower
skin layer (dermal layer) is referred to as deep pyoderma. These deeper
bacterial skin infections are usually associated with underlying causes as
opposed to irritants. Causes of deep pyoderma include hormone imbalances
(hypothyroidism, Cushing’s disease), skin cancers, malfunction of the
immune system, repeated trauma, and foreign bodies such as slivers of wood
or porcupine quills lodged deep into skin layers. Some external parasites
such as Demodex canis can also be a cause of deep pyoderma. Repeated
self-trauma due to skin allergies is an extremely common cause of both
superficial and deep pyodermas. Deep bacterial skin infections usually
appear as ulcerations/erosions of the skin with swelling and crusts;
sometimes draining tracts and swelling of skin tissue known as cellulitis
may also occur. If the skin in affected areas is squeezed, pus material may
ooze from weak areas in the skin surface.
Diagnosis: To diagnose a bacterial skin infection, a cytology
(examination of a sample under a microscope) of a sample from the affected
tissue is usually performed. A trained professional will be able to see cells
associated with bacterial infections (neutrophils), as well as the actual
bacteria in many cases. Identifying the underlying irritants or causes
associated with the pyoderma is often more difficult. Tests specific to a
suspected irritant or cause may be required to diagnose the underlying problem.
These tests might include skin scrapings for mange mites, cultures for fungal
infections, blood analysis for thyroid or cortisol hormone levels, skin
biopsies, dietary food trials, allergy testing, or imaging such as radiographs
or ultrasound. Additional information related to many of the above tests can be
found in Sections D and F.
Treatment: Treatment of bacterial skin infections is accomplished by both
removing the infection itself and removing the underlying reason the infection
is present. In cases of superficial skin infections, the irritant of the skin
(shampoo or cleaner, etc.) may easily be avoided. In other cases such as
repeated self trauma due to allergies, the offending cause may be extremely
difficult to identify, let alone avoid. Each situation must be dealt with on an
individual basis, with the help of a veterinarian.
Treatment of the infection itself is accomplished primarily with antibiotics.
A large variety of antibiotics exist which have effectiveness against most
pyodermas. Based on efficacy, antibiotics for use in treating bacterial skin
infections are categorized into "First Line" antibiotics, "Second
Line" antibiotics, and "Third Line" antibiotics. First Line
antibiotics are those which are effective 75-85% of the time and include
chloramphenicol and sulfa antibiotics such as Primor. First Line antibiotics
should always be used first in mild to moderate cases of superficial pyodermas
or where the infection is limited to a small area. Second Line antibiotics tend
to work in 90-95% of cases and include clindamycin
(Antirobe), some penicillins
such as Clavamox, and enrofloxacin
(Baytril). This category contains antibiotics
which have specific indications for use such as puncture wounds (for which
Clavamox is commonly used) and severe infections of the ear (for which Baytril
is often very effective). Third Line antibiotics are effective 98-100% of the
time and should be reserved for severe or generalized, deep pyodermas. Third
line antibiotics are made up of the cephalosporin antibiotic family. Cephalexin,
cefadroxil, and cephradine are members of this drug family. To avoid the risk of
developing resistant strains of bacteria, these third line antibiotics should be
used only when necessary.
Fungal Skin Infections:
Introduction: There are several types of fungi which can infect the skin
of dogs. Most fungal skin infections can appear identical to other types of
infections (bacterial pyoderma and demodectic mange). Therefore, specific
diagnostic testing should always be performed on a suspected fungal skin
infection to ensure an accurate diagnosis and treatment.
- Dermatophytosis (ringworm): Dermatophytes are a "keratinophilic"
(skin-loving) species of fungi which are responsible for the commonly known
syndrome "ringworm." Because the disease is not caused by a worm
at all, this term is rather inaccurate.
There are at least 20 different species of
dermatophytes which have been found to cause skin infections in dogs; however,
the vast majority of cases are infected with one of two species: Microsporum
canis and Trichophyton mentagrophytes.
Clinical Signs: Dermatophytosis in the dog appears very similar to other
infections of the skin. It is practically impossible to tell the difference
between dermatophytosis, demodectic mange, and some types of bacterial pyoderma.
Generally these fungal infections appear as areas of hair loss, with flaky,
crusty, irritated skin. These areas usually cause some degree of discomfort to
Transmission: Dogs can get ringworm in several ways. They can get the
fungi directly from other animals, including rodents, cats, dogs, and humans, or
from the soil. They can also be exposed to fungi found on surfaces, such as
brushes, blankets, and bedding.
Diagnosis: A dermatophytosis infection is diagnosed by performing a
culture of the hair from an affected individual. This is accomplished by taking
hair samples from the outside edge of a few of the lesions. The hair is then
placed on fungal specific media and any dermatophytes are allowed to grow. Most
culture results can be performed and interpreted by a veterinarian. Results may
take up to 10-14 days to provide an accurate answer. Other techniques commonly
used include a Wood’s lamp test and direct microscopic examination of hair and
scales of affected animals. Wood’s lamp testing involves close examination of
the skin of the animal with a special light which causes the hair and skin to
fluoresce a bright apple-green color if the pet is infected with a dermatophyte.
Wood’s lamp testing is only accurate in about 50% of cases. Direct microscopic
examination with the aid of potassium hydroxide preparations is also done. This
procedure, however, is time consuming and a positive diagnosis may be made in
only 50-60% of cases.
Treatment: There is a large variety of medications and treatment options
available for dermatophytosis therapy. Most often, a combination of several
types of therapy is utilized for maximum results.
- Affected areas should be clipped; cases with widespread lesions should
receive whole-body clips. This may worsen the problem initially.
- Whole-body topical therapy should be used in all cases. Shampoos (chlorhexidine,
miconazole, or iodine based) and dips (lime sulfur, sodium hypochlorite, and
chlorhexidine based) are types of effective whole-body topical therapy which
can be used.
- Systemic therapy (treatments going to the entire body) should be used in
many cases. Systemic treatments include griseofulvicin, itraconazole, and
ketoconazole. Because griseofulvin is teratogenic (causes severe birth
defects), it should NEVER be used in pregnant animals and must be used with
great caution in breeding females. Systemic anti-fungals are usually very
expensive especially for larger dogs.
Prevention and Public Health Concerns: Dermatophytosis is "zoonotic,"
which means that the disease is contagious to people. Care should be taken when
a pet is diagnosed with dermatophytosis. Follow the veterinarian’s
instructions when treating ringworm. Keep the dog’s skin healthy. Because
certain conditions encourage fungal growth, do not allow the dog’s skin to
remain damp and dirty. If ringworm is identified on the dog, all bedding, combs,
brushes, and cages must be thoroughly cleaned and disinfected. A 1:10 dilution
of household bleach can be used. The fungal spores remain viable for up to 18
months in the environment. Frequent washing of hands, bedding, and clothing
which comes into contact with the affected animal is very important. A thorough
vacuuming of carpets, vents, and rugs is also essential. Steam cleaning carpets
may also help. A physician should be contacted if people in the household become
affected with skin abnormalities.
* For additional information on ringworm infections in humans, refer to
Sporothrix schenckii is a fungus which causes skin
infections in dogs worldwide on a sporadic basis. In dogs, sporotrichosis is
usually associated with a puncture wound caused by a splinter of wood or thorn.
This disease tends to affect hunting dogs and other dogs which spend time
outdoors in contact with trees, bushes, and shrubbery.
Affected animals have multiple nodules of infection in the
skin and tissues underlying the skin. These nodules may be ulcerated and
crusted, and may have a draining discharge. If a limb is affected, the infection
may spread upward toward the body and may cause inflammation and infection to
occur in the lymphatic vessels and lymph nodes which are closest to the affected
limb. Secondary bacterial infections can occur.
Diagnosing this disease can be challenging in dogs. At body
temperature, Sporothrix schenckii lives as a yeast form that can be seen
on cytology when present. The challenge in dogs, however, is that relatively few
yeasts are present in the nodules, and they can be difficult to find. If
cytology is unhelpful in yielding a diagnosis of sporotrichosis, other
diagnostic testing is available. Fungal culture is probably the most commonly
successful diagnostic tool in the diagnosis of sporotrichosis; results may take
several days to a couple of weeks before they are available. Submission of a
sample of tissue for histopathology is another method of diagnosis; however, it
may be difficult to find the fungal organisms present in the sample. When all
other attempts at diagnosis have failed, immunofluorescence staining of
discharge or tissue may be performed by the Centers for Disease Control and
Prevention (CDC) in Atlanta, Georgia.
Treatment of Sporothrix schenckii infections may be
accomplished with the use of a supersaturated solution of potassium iodide (SSKI).
This solution should be given orally and then continued for at least one month
after the nodules completely subside. Recurrence of infection is common when
treatment has not been administered for a long enough period of time. Side
effects of SSKI include vomiting, lethargy, weakness, and nasal discharge. If
side effects are severe, alternative therapy may be offered. Such therapy
includes ketoconazole or itraconazole, both of which are general antifungal
drugs. Antibiotics for secondary bacterial infections should always be a part of
therapeutic plans for sporotrichosis.
Blastomycosis is a fungal disease of animals and people which
is termed "systemic," meaning it affects many body systems. Studies
have found that young, large breed, male hunting dogs are most at risk of
The organism which causes blastomycosis is called Blastomyces
dermatitidis and lives primarily in the Mississippi, Ohio, and Missouri
river valleys; the mid-Atlantic states of Virginia, North and South Carolina,
and Tennessee; and the northern parts of Georgia and Alabama.
Approximately 20-40% of dogs with blastomycosis
have skin involvement. Other organs and systems which are commonly affected
include the lungs, bones, eyes, brain, reproductive tract, and urinary tract.
Animals (and people) that spend time outdoors become infected by inhaling fungal
spores. Infection with Blastomyces dermatitidis can be a life-threatening
illness, especially if there is brain involvement or severe lung disease.
Permanent blindness may result in dogs with eye involvement. Skin lesions, if
present, are usually seen as areas of ulceration with drainage, abscesses, or
thickened inflamed skin. The skin lesions may occur anywhere on the body, with
the face, nail beds and nose being the most commonly affected areas.
Blastomyces dermatitidis fungal infections can be diagnosed
by histopathology, cytology or both. The organism usually is seen in more than
50% of histopathology or cytology specimens if they are obtained and prepared
properly. Serology can be used to confirm the diagnosis after the organisms have
been visually identified. In dogs, the agar-gel immunodiffusion test (AGID) is
currently the most accurate serology test available for diagnosing blastomycosis
in dogs. Because it cannot distinguish between past exposure and current
infection, the AGID test is unhelpful once an animal has recovered from
Treatment of blastomycosis is expensive, but the prognosis for
survival is generally good as long as the animal does not suffer from either
brain involvement or severe lung infection. However, the prognosis for recovery
of vision in dogs with severe eye infections is guarded, and some dogs are
permanently blind following blastomycosis infections. Amphotericin B,
fluconazole, and itraconazole are all antifungal drugs which have been used
successfully in treatment of blastomycosis. Itraconazole is generally used as
the drug of choice, but amphotericin B can be very effective in dogs which do
not respond to itraconazole therapy. Amphotericin B is toxic to the kidneys, and
blood monitoring of kidney function should be routine while an animal is
receiving this antifungal drug. Relapses can occur, especially in dogs which
have had severe lung involvement. No vaccine is currently available for
prevention of blastomycosis.
Parasitic Skin Infections:
When we speak
of the various parasites which infect the skin of either people or animals, they
are specifically referred to as "ectoparasites," meaning parasites
which remain on the surface. In contrast, "endoparasites" are those
parasitic organisms whose life cycles favor the internal environment of the
body. The following are some of the most common ectoparasites found in pets.
Fleas are one of the most common external parasites seen in
dogs. Because they do better in hotter, more humid environments, fleas are
more of a concern in some areas than others. Fleas lay their eggs on the host
dog, but the eggs do not stick well to the skin or hair coat, and tend to fall
off into the dog’s environment. After hatching, the flea larvae must again
find a host. Fleas are an obligate parasite, which means that they cannot
survive for long on their own away from a host.
A range of problems are seen in dogs with flea
infestations. Minor infestations may go unnoticed in some cases or may cause
some itching (pruritus). In the very young or debilitated animal with more
severe infestations, blood loss may be significant enough to cause anemia.
However, the most significant problems noted with flea infestations in dogs
are hypersensitivity reactions to the flea bite itself. Dogs which develop
fleabite hypersensitivity usually suffer severe itching (pruritus), and may
develop hair loss, thickened and/or discolored skin, and secondary bacterial
infections. Only one to two flea bites per week may be sufficient in
supersensitized pets to perpetuate the problem. Dogs with underlying allergies
(atopy, food sensitivity) are prone to fleabite hypersensitivity.
Diagnosis of a flea infestation is usually made by noting the
actual fleas on the skin of the animal or in the environment where the animal
lives. Pinpointing a fleabite hypersensitivity problem, however, can be much
more challenging, since a very minor infestation may be all that is present in
such cases. One important piece of information in differentiating flea
infestations from and other conditions is the pattern of hair loss and itching
on the dog’s body. Most flea problems occur on the back half of a dog’s
body, especially affecting the abdomen, anal area, base of the tail, back of
the thighs, and lower back areas. The head is usually spared in most fleabite
hypersensitivity reactions. Flea combs may be used by veterinarians or pet
owners to comb out evidence of fleas. Flea dirt is often combed out and can be
distinguished from other debris by placing the suspected flea dirt on a
moistened napkin. Because flea dirt is the excrement from a parasite that
consumes blood, it will leave light red stains on the napkin.
Other tests, including a CBC and skin biopsies, can be used to help identify
fleabite hypersensitivity. A specific type of white blood cell called an
eosinophil is commonly seen in both a blood sample (CBC) and in a skin biopsy.
Another aid for a veterinarian diagnosing fleabite hypersensitivity, can be
giving an injection of flea allergen directly into the skin and looking for an
Finally, specific flea treatment products are often administered and the
animal observed to see how it responds to the treatment. If the pet responds
favorably to the treatment, a diagnosis of flea infestation can be made. Using
treatment as a "diagnostic approach" can be done because most
treatment products are generally considered safe and affordable.
Treating flea infestations primarily focuses on
removal of the fleas from both the animal and the animal’s living
environment. First, eliminate fleas from the animal. There are many available
products, some of which are obtainable through a pet store (over the counter),
while others are prescription drugs and are obtainable only through a
veterinarian. Over the counter products which may be helpful include flea
combs, flea collars, sprays, dips, powders, and shampoos. Insecticidal flea
collars are generally more effective than ultrasonic collar devices at
reducing flea infections. Sprays usually have rapid action, but may be
difficult to apply in a thorough and consistent manner. Flea dips are
generally rapid-acting and long-lasting; dips may be given through a pet
grooming facility or at home. Flea powders are effective but messy, and
usually vary on how long they will last. Flea shampoos are usually good for
rapid killing of fleas, but have no residual (lasting) benefits.
In general, the over-the-counter products alone are probably insufficient
for adequately treating a dog with fleabite hypersensitivity. Prescription
products available through a veterinarian are usually of great benefit to dogs
with fleabite hypersensitivity problems. These products can be used for
treatment and prevention. Many of these products not only kill fleas, but are
effective against a variety of other parasites including ticks, mites,
intestinal parasites, and heartworm larvae. Pour-on (drip-on) formulations
that are available include Frontline, Advantage, and
Revolution. Oral tablets
are also available and include Program, Sentinel, and Capstar (new in 2001).
Each of these prescription products is approved for flea control as well as
many other parasites affecting dogs.
Second, eliminate fleas from the living quarters and bedding of the dog.
This is accomplished with a thorough washing of carpets, rugs, and bedding.
Followed by vacuuming furniture, beneath furniture, baseboards, and even
calling in a commercial exterminator. Some advocate the use of foggers;
however, foggers may not be effective under furniture and it is usually
necessary to utilize one fogger per room of the house. Some products (Program)
for use on the affected animal(s) will prevent flea development and keep the
eggs from hatching in the environment.
An effective treatment plan must involve three things:
- Treating the pet’s environment
- Treating the affected pet
- Treating all other pets that have contact with the affected pet
(Failure to thoroughly address any of these three areas can result in
continued and repeat flea infestations.)
* For more information on flea infestations in both humans and pets, see
Ticks are a common bloodsucking ectoparasite which cause skin
disease in dogs. There are many different species of ticks that can be found
throughout the world. The most important health problem associated with ticks
is not the skin disease they cause, it is the disease they might transmit.
Ticks are responsible for transmitting a large number of microbial diseases to
dogs and other species, including man. Some of the diseases ticks are
responsible for transmitting may be life-threatening to dogs and people.
Babesiosis (piroplasmosis), Lyme disease, ehrlichioisis (tropical canine
pancytopenia), Rocky Mountain spotted fever, tularemia, Q fever, and Colorado
tick fever are all infectious diseases which are transmitted by ticks.
Ticks may attach themselves to any part of a dog and often
cause a local inflammatory reaction in the skin at the site of attachment.
Toxicosis (tick paralysis) and severe blood loss in massive tick infestations
When attached to an external location on the dog, the cause of
the problem is usually readily identified, because the tick is quite large
when engorged with blood. Sometimes, the tick may attach itself in a more
difficult area to access, such as inside the ear canal. This can make
diagnosing this problem more complicated.
Once the problem is identified as an attached tick, removal must
be performed. Because mouthparts have usually not become embedded in the skin,
removal is usually quite easy if done within the first hours after attachment.
Cautiously removing each individual tick with thumb forceps is acceptable for
some species of tick; however, other species secrete a type of cement which
may make complete removal much more difficult. Leaving mouthparts embedded in
the skin may cause irritation and secondary bacterial infections. If the tick
cannot be safely removed, there are many different products that are very safe
and effective at treating tick infestations. These products are listed below
Treatment for the various microbial diseases ticks can transmit
is often complicated and costly. Because of this, prevention of tick
infestations is of great importance. A variety of quality products exist which
may be administered before a dog is taken into an area known to harbor ticks.
Over the counter products which may be helpful include collars, sprays, dips,
powders, and shampoos. Insecticidal flea/tick collars are generally more
effective than ultrasonic collar devices. Sprays usually have rapid action,
but may be difficult to apply in a thorough and consistent manner. Dips are
generally rapid-acting and long-lasting and may be given through a pet
grooming facility or at home. Tick powders are effective but messy and usually
vary on how long they will last. Shampoos are usually good for rapid killing
of ticks, but some have no residual (lasting) benefits. Prescription products
are generally extremely effective, long-lasting, and safe. Pour-on (drip-on)
formulations that are available include Frontline, Kiltix, and Revolution. The
Preventic Tick Collar, available through veterinary clinics and hospitals,
claims to be the only flea and tick collar that detaches and kills ticks
* For additional information on tick borne diseases see page F998.
Generalized mite infections in dogs are
usually grouped under the common disease term of "mange." Mange is
then more specifically broken down based on the species of mite which is
responsible for the infection. In dogs, the three types of mange most commonly
encountered are demodectic mange (caused by Demodex canis), sarcoptic
mange (caused by Sarcoptes scabiei), and "walking dandruff"
(caused by Cheyletiella yasguri). A fourth type of mite which infects
dogs is Otodectes cynotis, causing a local infection in the ear canal and
Introduction and Causative Agents:
This type of mange can be a particularly
difficult disease to manage. Demodex canis is found in the skin in
small numbers of most normal dogs. Pups acquire Demodex mites from
their mothers when nursing. Animals which develop demodectic mange are
thought to have a deficient immune system which allows larger than normal
numbers of mites to grow.
- Demodectic mange (demodecosis):
Signs usually include hair loss, crusting, and
mild to intense itching. The region around the eyes, mouth, and feet are
frequently affected; however, the infection may occur on any area of the body.
Localized or focal demodecosis is a minor type of mite infection. These focal
infections can be found as small areas or patches of hair loss, flaky skin,
and inflammation. They can appear as one or multiple lesions.
Diagnosing demodectic mange is accomplished by first
taking deep scrapings of the skin. When taking a skin scraping looking for
demodectic mange, it is important to get a small amount of blood with the
sample. The reason for this is that the mites live deep in the hair follicles.
If small capillaries of blood are reached/ruptured with the scraping, the
scraping is deep enough to include these mites in the sample. The mites
themselves are then identified microscopically, making the diagnosis
Generalized (whole-body) infections can (and frequently do) affect the
entire body of the dog and may affect puppies or adults. In these infections,
the skin becomes coarse, dry, and red (these infections are sometimes referred
to as "red mange"). Puppies that are affected with whole-body Demodex
canis infections are quite often purebred and have an inherited defect of
the immune system which allows growth of the mites. Adults that are affected
with whole-body Demodex canis infections usually have an underlying
illness which causes suppression and weakening of the animal’s immune system
allowing growth of the mites. Such diseases may include hypothyroidism,
Cushing’s disease, diabetes mellitus, or cancer. Secondary bacterial
infections of the skin are very common with generalized demodectic mange. In
extremely severe cases, the secondary bacterial infections can spread to the
bloodstream (septicemia) and may lead to death of the animal.
Except for the focal form, treatment of demodectic
mange is complicated and often difficult. Because it can resolve on its own,
therapy is often not necessary for the focal form. Topical products like
benzoyl peroxide gel or benzoyl benzoate ointment (Goodwinol ointment) can be
used if treatment is required in these focal infections. Antibiotics may be
used if secondary bacterial infection occurs.
The focal form carries the best prognosis for full
recovery, followed by the adult generalized infections which may be curable if
the underlying disease process can be resolved or managed. The puppy
(juvenile) generalized type of infection is the least favorable, with most
requiring very aggressive treatment for management of the disease and few ever
achieving full recovery.
Treatment of the generalized forms is always necessary. Steroid therapy for
itching is unacceptable because it almost always makes the infection worse by
further weakening the immune system. Adults with generalized infections should
have the underlying problem addressed and properly managed to help strengthen
the immune system. Affected females should be spayed as soon as possible,
because estrogen (a steroid type hormone) can also weaken the immune system
and should be eliminated. Affected puppies usually carry an inheritable defect
in the immune system; these puppies should be neutered or spayed to prevent
passing on the defect.
Amitraz (Miteban) dips are the only FDA-approved specific treatment for
demodectic mange in dogs. Amitraz dips should be performed every week in
severe cases and every 2 weeks in mild to moderate cases. Skin scrapings
should be performed every 3 weeks to assess the effectiveness of amitraz
therapy. Dips should continue for 4 weeks after scrapings are negative for any
mites. Other drugs that can be used include ivermectin (doses used are fatal
to Collies and Shetland sheepdogs!) and milbemycin oxime (Interceptor).
Ivermectin is now considered the treatment of choice in dogs which have failed
to respond to amitraz. Finally, antibiotics are frequently utilized to fight
secondary bacterial infections.
- Sarcoptic mange:
mites have a preference for a certain species of host. For example, some
types of Sarcoptes scabiei prefer humans, while others prefer dogs or
pigs. While a mite infection can spread from one species to another (i.e.
from a dog to a person), the resulting infection is usually mild and goes
away on its own. When an infection occurs in the species of preference,
however, the resulting skin problems can be extremely severe.
- Introduction and Causative Agent:
Sarcoptic mange in dogs usually takes 1-2
weeks from exposure before clinical signs begin. Itching usually intensifies
over the next couple of weeks and may become one of the most agonizing skin
conditions to affect dogs. The mites seem to prefer hairless areas on the
body such as elbows, hocks, chest, abdomen, and tips of the ears. This mite
causes a reddened, crusting appearance to the skin. Secondary bacterial
infections of the skin are common. Some dogs can have significant
inflammation and itching with relatively few mites. This supports the idea
of a hypersensitivity reaction similar to fleabite hypersensitivity (see
above). Sometimes sarcoptic mange can occur without the typical crusting and
reddening of hairless areas on the body; usually these dogs have intense
itching, but no other clinical signs. These cases are referred to as "sarcoptes
incognito," and may be more difficult to diagnose.
Diagnosing sarcoptic mange may be more difficult
than demodectic mange, but it is usually easier to manage. Multiple skin
scrapings are usually performed; if mites or mite eggs are seen, a diagnosis
is established. Fecal flotations may also be helpful in identifying mites
and eggs that may be ingested while a dog is grooming itself. However, mites
and/or eggs are seen in only 20-50% of affected dogs. In challenging cases,
specific mite treatment products are often administered and the animal
observed to see how it responds to the treatment. If the pet responds
favorably to the treatment, a diagnosis of sarcoptic mange infestation can
Treatment of sarcoptic mange is usually very
successful. Weekly lime sulfur or amitraz (Miteban) dips can be very
helpful; usually treatment for 4-6 weeks is sufficient for resolution.
Ivermectin is a very effective drug which may be used either orally or as a
series of subcutaneous injections; however, it is important to remember that
this drug is fatal to some breeds of dog at the doses needed to treat
sarcoptic mange. Herding breeds such as Collies, Shetland sheepdogs, Old
English sheepdogs, and Australian shepherds may have very severe reactions
to ivermectin and should be treated with an alternate therapy. Milbemycin
oxime (Interceptor) and selamectin (Revolution) have been used successfully
for cases of sarcoptic mange and may be used in those breeds sensitive to
ivermectin. Interceptor is given orally while Revolution is a pour-on type
treatment. Most cases appear to respond to a single treatment of Revolution.
Treatment of all animals in contact with the affected individual is of great
importance for complete control and resolution of sarcoptic mange regardless
of the type of therapy used.
- Cheyletiella yasguri:
This third type of mange mite which infects dogs.
It is somewhat lesser known than either demodectic or sarcoptic mange. This
mite is able to live in the environment for up to 10 days, sometimes leading
to re-infection of treated animals. Cheyletiellosis is considered zoonotic,
being highly communicable to people as well as other animals.
Cheyletiella yasguri is a rather large
mite which tends to cause flaking and dandruff on the back of dogs. As the
mites move, the large flakes of dandruff will move around as well. Because
this movement is visible to the naked eye, the term "walking
dandruff" is used. This walking dandruff is typical in puppies with Cheyletiella
yasguri infections. Itching is severe to completely absent.
Diagnosis of cheyletiellosis is made by direct
visualization of the mites and/or their eggs. Mites and eggs may be collected
from an infected individual by skin scrapings, tape preparations, combings,
vacuum techniques, or analysis of the feces.
Treatment of cheyletiellosis may include weekly lime
sulfur dips for 3-6 weeks, oral ivermectin treatments weekly for 4-6 weeks, or
subcutaneously injected ivermectin every 2 weeks for 3 treatments. Ivermectin
given at doses needed to treat cheyletiellosis may be fatal to herding breeds,
especially Collies and Shetland sheepdogs! Many medications used to control
fleas may also be successful at treating Cheyletiella yasguri
infections. Because it can live off of the host for a longer period than most
mites, maintaining a clean environment is very important in successful
management of this type of mange. Frequent vacuuming of carpets and rugs,
washing of the bedding, and treatment of all dogs and cats in contact with an
infected pet are all important in helping to prevent re-infection of treated
* For additional information on mites in humans and pets, see F998.
Dark waxy debris is common with infestations
of Otodectes cynotis and intense itching of the ears usually
accompanies such infections. Some dogs which suffer from ear mites may shake
their heads so violently because of irritation that they develop an aural
hematoma (a very painful swelling of the ear pinna or thin, floppy part of
the ear). Secondary ear infections with bacteria and/or yeast are common
with ear mites. Ear mites are also a common underlying cause of recurring
ear infections in dogs.
- Otodectes cynotis is a common mite which is found mainly in the
ear canals and adjacent skin of dogs, cats, and ferrets.
Diagnosis of ear mite infections is made by
observing the mites using a microscope. A cotton-tipped swab is introduced
into the ear canal and a sample of the dark waxy debris is retrieved and
examined under magnification. Response to therapy is also becoming more
important as a diagnostic tool, because recent research indicates that ear
mites in dogs are more commonly missed with the swab technique described
Many treatments for ear mites exist, some of which
can be found over the counter in pet shops and stores. Because ear mites are
very contagious between animals, it is important to treat all in-contact
dogs and cats as well as the affected pet. Regardless of the treatment
selected, a thorough cleaning of the ears is the first step to clearing up
an ear mite infection. Rotenone-based or pyrethrin-based ear drops or washes
can be used with some success. Ivermectin administered either subcutaneously
or directly into the ears may be used, but must be avoided in herding breeds
especially Collies and Shetland sheepdogs. Finally, selamectin (Revolution)
has recently been approved for treatment of ear mites in dogs and puppies,
and appears to be a very safe, effective, inexpensive, and simple means of
treating Otodectes cynotis infections.
Most lice are extremely species-specific,
which means that they are adapted to one type of host animal (or human) and are
unlikely to be contagious to other species of animals. They can be, however,
very contagious to other individuals within the same species. One exception to
this rule is Pthirus pubis, the human crab louse, which a family dog may
occasionally contract from people. Some cases of Pthirus pubis infections
involve the entire family, including the family dog. A veterinarian must
approach such situations tactfully, explaining that the dog cannot be the
primary source of infection for this particular parasite. More commonly, dogs
with lice infections are diagnosed with Trichodectes canis (the canine
chewing louse), Linognathus setosus, or Heterodoxus spiniger.
Introduction and Causative Agents:
Lice are parasites of the skin which cause mostly superficial skin
inflammation and itching.
Diagnosing an infestation with lice is made by identifying the
parasite using a microscope. Careful observation of the anatomy of the louse
will aid a professional in identifying the specific species causing the
infection. As demonstrated in the example in the preceding information,
identification of a specific species of louse is important in order to determine
the most likely source of infection and may aid in preventing re-infections.
Treatment of lice infections in dogs is accomplished with the use
of carbaryl shampoos or dioxathion shampoos, sprays, or dips. Usually, treatment
is administered and repeated weekly until the lice infestation has resolved. Two
or three treatments are usually sufficient.
Allergic Skin Disease
Introduction: Allergic skin disease is
extremely common in dogs. Allergic skin disease is broken down into three major
categories based on how the offending substances, which cause the allergic
reaction, enter the body. Recently, how these category headings are broken down
has come into some controversy. This is because a given substance that causes an
allergic reaction may actually enter the body through many different avenues. It
is actually quite important to understand this when treating an allergic skin
condition. In general, allergies result from an exaggerated response to a
foreign substance (allergen) that the immune system perceives as a threat to the
- Atopic or Allergic Inhalant Dermatitis:
Introduction: The term allergic inhalant dermatitis implies that the dog
inhales the substances which then lead to a reaction in the skin. Atopic
dermatitis is a less restrictive term, implying that the allergic reaction is
a response to ordinary environmental substances. Many studies indicate that
atopic dermatitis may result from not only inhalation of these ordinary
substances, but also through ingesting these substances or when these
substances directly contact the skin. Because of this new understanding, the
term allergic inhalant dermatitis is falling out of favor. Atopy is a general
term used to describe these types of allergic reactions.
Atopy is often considered an inherited problem passed on through genetics.
Certain dog breeds to tend to develop atopic dermatitis more frequently than
others. West Highland white terriers, English setters, Cairn terriers, Wheaten
terriers, and Fox terriers are probably the five most allergic dog breeds.
Other breeds which are frequently diagnosed with allergic skin disease include
Labrador retrievers, cocker spaniels, and Chinese shar peis. Dogs with atopy
usually begin to experience skin problems somewhere between the ages of 1 and
Causative Agents: Dogs can be allergic to a variety of things including
regional pollens, house dust, house mites, air-borne molds, human dander, and
often food proteins to name a few. All of these are considered allergens or
substances that produce an allergic reaction. When one of these substances
contacts the animal, the immune system produces several types of antibodies
known as immunoglobulins. Most of these have the absolutely crucial function
of fighting infection. One specific type of antibody, known as Immunoglobulin
E (IgE) plays a significant role in allergic reactions. Basically, the immune
system of dogs with atopy over reacts and a hypersensitivity reaction results.
This hypersensitivity reaction produces excess IgE and causes the release of
histamine and other substances. IgE is generally found in very high levels in
dogs which suffer from atopy.
Clinical Signs: The signs of atopy include mild to severe itchiness (pruritus)
and skin redness. Hair loss (alopecia) and thickening of the skin are also
possible. Secondary bacterial or yeast infections are common and may result in
drainage of pus, crusting, and further itching. Areas of a dog which are most
frequently affected by atopy include the feet, face, ears, axillary (armpit)
areas, and inguinal (groin) areas. Atopy may or may not be seasonal, depending
upon the offending substance causing the reaction and the individual animal.
Reactions to pollens tend to be worse in the late summer, whereas reactions to
house dust may be worse in the winter when windows are left closed and
furnaces are turned on, blowing dust from air vents. In many dogs, the
seasonal nature of atopy may steadily progress to a constant problem, with no
relief as the seasons change.
Diagnosis: The diagnosis of atopy is somewhat of a challenge. In many
situations, no formal testing is done, and the diagnosis is made based on
history, clinical signs, and response to treatment. Testing is available,
however, and can be extremely beneficial for dogs suffering from atopy.
The intradermal skin test is generally accepted as the best test available for
the diagnosis of atopy. To perform this test, an experienced veterinarian
(usually a veterinary dermatologist) injects small blebs of reagents/allergens
to which dogs are known to react directly into the skin. Allergic dogs will
react by forming a lump or "wheal" in the area associated with the
specific injection(s) they are allergic to. Sedation is generally very helpful
when performing the test and helps to decrease interference with natural
steroid release from an excited or anxious animal. The pet undergoing an
intradermal skin test should not be treated with any corticosteroids (i.e.
prednisone) for at least 6 weeks prior to testing. The steroid can prevent the
skin from reacting to the offending reagent(s). This test is very dependent
upon the experience of the professional performing the procedure and the
interpretation of the results.
The second type of testing commonly used in the diagnosis of atopy is
serologic allergy testing. Currently, three major types of serology tests are
available which can be used for diagnosing atopy: ELISA (enzyme-linked
immunosorbent assay), RAST (radioallergosorbent test), and liquid-phase
immunoenzymatic assay (VARL). Blood from a suspect atopic dog is sent to a
laboratory for measurement of IgE levels against specific allergens. A
detailed history of the condition and the region of the country where the dog
resides are also included. Testing is performed on the blood using a variety
of allergens (regional pollens, house dust, house mites, air-borne molds,
human dander, and often food proteins) to which the dog may be reacting. These
tests measure IgE levels in the animal’s blood and report any allergens
where there is a high IgE response.
As a side note, a smaller and much quicker ELISA test, called the Allercept
E-Screen IgE test, is currently available through Heska Laboratories. This
test (which can be run in a veterinary clinic in 5 minutes) shows the total
IgE levels in a dog’s blood sample and may indicate what animals require
more extensive and specific testing.
Histopathology of a biopsy sample from affected skin may be used as an aid to
help in the diagnosis of atopy, but generally cannot provide a specific
diagnosis of atopy.
Treatment: Treating atopy is another area of challenge. Treatment is
broken into 2 major categories: immunotherapy and non-immunotherapy.
- Immunotherapy, also known as hyposensitization, consists of
desensitizing the dog’s immune system to the allergen or allergens which
cause the allergic reaction. In order to offer this type of therapy, either
intradermal skin testing or serologic allergy testing must be performed in
order to specify the exact offending allergens to be desensitized against.
The way hyposensitization works is extremely complex. Small, measured
amounts of the specific allergen(s) to be desensitized against are injected
regularly under the skin. These injections may be administered at home or in
a veterinary hospital. A specific schedule with the frequency and amount of
each injection is outlined and strictly followed. Studies show that between
50% and 80% of treated animals have a good to excellent response.
Immunotherapy has been described as the mainstay of atopy treatment in dogs;
however, in reality it is underutilized as a therapeutic tool. This is
probably due to both the cost involved in the testing and the immunotherapy
itself. Further research needs to be done in the area of canine
immunotherapy to help better understand all the factors which affect the
success of treatment. This will help the veterinarian select the best
candidates for a successful response to this type of therapy.
- Non-immunotherapy is a collection of medications used in the
treatment of atopy and other types of allergies. Each category will be
briefly discussed here under the heading of atopy, but it should be
remembered that all types of allergies may respond to one or a combination
of the medication types listed.
- Corticosteroids: Corticosteroids are a class of powerful
anti-inflammatory drugs, which are commonly used in the control of canine
atopy. Corticosteroids given systemically (orally or by injection) are
necessary to help control atopy in a large number of cases, although they
are usually less effective in helping to control food allergies in dogs.
Prednisone, prednisolone, methylprednisolone, triamcinolone, and sometimes
dexamethasone are often used in dogs. Corticosteroids are generally
inexpensive, but have undesirable side effects. These side effects include
the excessive need to drink water and urinate, appetite changes, behavior
or personality changes, and liver irritation. Because of these side
effects, the main goal with corticosteroid therapy is to control the
condition adequately on the lowest possible drug dose. Usually, the right
dose given orally, every other day is both effective and minimizes
undesirable side effects. Many of the following medications may be used
with the attempt to reduce the need for corticosteroids.
- Antihistamines: Antihistamines are a class of anti-itch therapy drugs
used commonly in people with allergies. Antihistamines are only beneficial
in about 20-30% of dogs with atopy or other types of allergies. There are
several antihistamines available, and it is generally very difficult to
predict which, if any, will be effective in any given dog. Antihistamines
may be synergistic (more effective if given together than separately) with
essential fatty acids. Some available antihistamines which may be utilized
in the treatment of allergic skin problems include diphenhydramine
(Benadryl), hydroxyzine, chlorpheniramine (Chlor-Trimetron),
cyproheptadine, and clemastine (Contac). It has been suggested that a
first attempt at treating a dog with atopy (if non-immunotherapy is to be
pursued) begins with essential fatty acid treatment and then multiple two
week trials of several different antihistamines. If a combination is found
to be beneficial to the dog, this therapy may be used either exclusively
or in combination with other medication based on need. If no antihistamine
is found to be effective, corticosteroids are then used.
- Essential fatty acids: Essential fatty acids (EFA) are composed of Omega
3 and 6 fatty acids, with the most emphasis on the Omega 3 fatty acids to
best control itching in dogs. EFAs are effective in 10-20% of patients
and should be given for at least 3 months to observe maximal benefit. Some
diets supplemented with Omega 3 fatty acids have shown promise in helping
to reduce itching in dogs with atopy. EFAs are considered to be very safe,
with adverse side effects occurring only very rarely. EFAs are generally
given daily as a capsule or liquid.
- Tricyclic antidepressants: There is a significant psychological
component to many allergic skin problems. This class of drugs works by
helping to minimize self-destructive behavior such as licking, chewing,
scratching, and biting.
Tricyclic antidepressants may also work more directly at reducing the
amount of pruritus (itching) experienced by dogs suffering from allergies.
Side effects of these medications can include drowsiness, heart rhythm
disturbance problems, and seizures (rarely). Some of the specific drugs
which can be used include amitriptyline, clomipramine, doxepin, and
fluoxetine (Prozac). Certain medications have undesirable interactions
with tricyclic antidepressants and should be avoided when treating with
this class of drugs. In general, these drugs produce positive responses in
about 20-25% of cases.
- Topical therapy: A large number of topical medications exists that can
be helpful in cases of atopy. Most of these products, however, must be
used along with other therapy and not as the sole treatment for allergies.
By far the easiest and most cost-effective is cool-water bathing, which
may give relief for up to 1-2 days. Other types of topical therapy include
shampoos/conditioners, lotions, and sprays. Shampoos which reduce pruritus
(itching) may contain oatmeal (see page G207), local anesthetics such as
pramoxine, antihistamines such as diphenhydramine, and corticosteroids
such as hydrocortisone. Cooling agents such as camphor and menthol may
also be helpful in replacing the itch with a cool sensation. Dry skin
increases the sensation of itching and may be alleviated with skin
moisturizing lotions, shampoos, or emollients such as fatty acids,
glycerin, and oatmeal. Sprays may contain antihistamines, corticosteroids,
or local anesthetics. Daily foot soaks with shampoos are particularly
effective in dogs which suffer primarily from itchy paws, while sprays may
be most effective for use in small problem areas.
- Dietary therapy: Dietary therapy is generally beneficial to those
animals suffering specifically from food related allergies (discussed
below); however, exceptions do exist. Among these exceptions are diets
containing essential fatty acid supplements (discussed above). For animals
that suffer from food allergies, dietary therapy is the primary treatment.
A variety of "low allergy" or hypoallergenic diets exist. Many
of these diets may be purchased as over the counter diets, while others are
sold only as prescriptions through veterinary hospitals and clinics. Many
of the diets available only by prescription through veterinarians are used
in the most severe cases. Cases that use the prescription diets tend to
have a greater success rate than those that use only the over the counter
diets. There are so many types of diets which may be used in food
allergies that no attempt will be made here to list them; see the section
on food allergies for more information on the properties of these
Introduction/Causative Agents: Allergic skin disease resulting from an
adverse reaction to food is responsible for up to 15% of all skin related
allergies in dogs. Food allergies along with food intolerances make up a broader
category known as food sensitivities. Food allergies are due to a reaction by
the body’s immune system to certain substances (allergens) in food. Food
intolerances do not involve the immune system and are usually due to certain
types of food such as dairy products. It generally takes some time for a dog to
develop an allergy to food, and some dogs may eat the same diet for years before
they begin to react to an ingredient. Allergens which are most commonly
associated with food allergies include beef, milk, soybean, chicken, pork,
yeast, corn, and wheat. There are no strong breed predilections for food
allergies in dogs, although according to some dermatologists, the retriever and
terrier breeds are probably the most commonly affected. Dogs first diagnosed
with food allergies tend to be younger, and more than 80% are affected at less than
3 years of age.
Clinical Signs: The signs of food allergy in dogs are similar to atopy. They
include moderate to severe itchiness of the skin in the feet, face, ears,
axillary (armpit), and inguinal (groin) areas. Up to 20% of dogs with food
allergies may suffer from persistent and/or recurrent inflammation and infection
of the ears only, with no other body areas affected. Only rarely do vomiting or
diarrhea accompany skin problems in dogs with food allergies. Like atopy,
secondary bacterial or yeast infections are common. Food allergies are not
Diagnosis: The diagnosis of food allergy is accomplished with a dietary
trial. During the trial, a diet with a limited number of possible food allergens
is fed for 6-8 weeks. Throughout the trial, additional food and food products
(table scraps, snacks, chew toys, or palatable medications) must be eliminated.
The diet itself can be either home-made or commercial, but must contain only
carbohydrates as a base and one protein type to which the dog has never or only
rarely been exposed. Such protein sources can include lamb, fish, duck, or
venison. The carbohydrate base is usually composed of cooked rice or potato and
is the main source of calories during the trial. Homemade diets are usually the
best. Commercial hypoallergenic diets such as Lamb & Rice can be used and
are generally successful in 75-80% of dogs with food allergies. If after 6-8
weeks, the dog has shown some improvement with a strictly followed dietary
trial, the diet is then continued until maximal improvement is noted. To confirm
the diagnosis, the patient is then given its previous diet. Clinical signs
should recur within 7-10 days. If there is no response to a diet trial after 6-8
weeks, then a different type of hypoallergenic diet may be fed. If the dog
continues not to respond to the dietary trials, then food allergies are ruled
out of the list of possible problems. Further testing may be necessary to
determine the correct diagnosis.
Treatment: Proper treatment for food allergic animals is life-long
maintenance with a diet that the animal can tolerate without experiencing skin
reactions. For life-long maintenance, it is best to have the dog on a high
quality, hypoallergenic commercial brand dog food; this is possible in most dogs
with food allergies, although some experimentation may be required to find a
brand and ingredient combination that will be well tolerated. Occasionally, a
dog may need to be maintained long-term with a homemade diet. Vitamin and
mineral supplementation may be necessary in such cases to avoid nutritional
deficiencies. Corticosteroids may be used in dogs with food allergies as a last
resort, although the success of this type of therapy is sometimes poor.
Allergic Contact Dermatitis:
Introduction: Allergic reactions to substances which directly contact the
skin can affect the general condition of the animal or may simply cause a local
reaction in the area of contact. Reactions which remain localized to the area of
contact are known as contact allergic reactions or allergic contact dermatitis.
It may become confusing when a dog experiences allergic contact dermatitis due
to a substance which has contacted the entire body such as a shampoo or body
rinse. These cases where the problem extends over the entire body may appear at
first to be a case of atopy (see above). Generally, most cases of allergic
contact dermatitis in dogs are a result of topical medication. Because of this,
the history is extremely important in helping the veterinarian pinpoint the
cause of the itching.
Causative Agents/Clinical Signs: Many cases of contact dermatitis are caused
by medications, shampoos, bedding, chemicals, cleaning agents, or other similar
products. When contact is made with these substances, the body’s immune system
reacts by changing the skin in the area where the contact is made. The ears,
abdomen, thighs, feet, tail, and chin are commonly involved. When an allergic
reaction occurs in these areas, the skin is red, inflamed, can be itchy (pruritic),
and have bumps or blisters (vesicles).
Diagnosis: To diagnose allergic contact dermatitis, a thorough history is
essential. Information on the types of medications or shampoos used recently,
bedding type, and any contact with chemicals, cleaning agents, or other similar
products is extremely helpful. Skin patch testing and environmental testing are
two lines of diagnostics which may be performed by an experienced veterinary
Treatment: The treatment of allergic contact dermatitis focuses primarily on
avoiding the substance/medication which led to the reaction. Corticosteroids may
be used either systemically or topically to relieve immediate itching and
Autoimmune Skin Diseases
Introduction: Autoimmune skin diseases
(also known as immune-mediated disorders) are best described as conditions in
which the body’s immune system is directly responsible for damage done to the
skin. Allergic skin disease is also traced to the immune system, but is a result
of a more indirect reaction. Allergies result from an exaggerated response to a
foreign substance (allergen) that the immune system perceives as a threat to the
body. Autoimmune skin disease is a result of direct attack by the immune system
on the skin itself. When compared to skin disease as a whole, autoimmune
disorders are much less common than either infectious or allergic skin disease.
Autoimmune diseases are broken down into primary and secondary disorders.
Primary disorders are those which develop spontaneously, independent of any
external triggers. Secondary disorders are a result of a triggered response,
traceable to a variety of stimulating factors such as certain drugs, bacteria,
or viruses. The following will discuss three major types of autoimmune diseases:
- Pemphigus Complex: There are 4 main varieties of pemphigus reported
in dogs: pemphigus foliaceous, pemphigus erythematosus, pemphigus vulgaris,
and pemphigus vegetans.
- Pemphigus foliaceous is the most
common form of the pemphigus complex seen in dogs. Akitas, chow chows,
dachshunds, bearded collies, Newfoundlands, Doberman pinschers, Finnish
spitz, and Schipperkes are breeds more frequently affected by pemphigus
foliaceous. A drug-induced, secondary form of pemphigus foliaceous is seen,
especially in response to sulfa-based antibiotics. This type of pemphigus
foliaceous may be more common in Doberman pinschers and Labrador retrievers
than other breeds. Pemphigus foliaceous primarily affects the face, feet,
and ears. Normal dark coloration of the nose may lose pigment and change to
pink or white. This may result in "photodermatitis."
Photodermatitis is a term which implies a skin disorder that worsens with
exposure to sunlight.
- Pemphigus erythematosus is usually thought of as a form of
pemphigus foliaceous which is confined to the face and ears. Like pemphigus
foliaceous, loss of pigment in the nose and resulting photodermatitis may
occur. Collies and German shepherds are more commonly affected.
- Pemphigus vulgaris is extremely uncommon. This is fortunate,
because it carries the poorest prognosis of the pemphigus complex. Many
cases of pemphigus vulgaris are unmanageable or manageable for only a short
period of time. Frequently, euthanasia is the ultimate outcome. It does not
seem to be associated with any age, sex, or breed types. The feet, face,
mouth, armpit (axilla), groin (inguinal area), anus, vulva, and prepuce may
be affected. Many cases develop ulcers and inflammation in the mouth,
leading to difficulty eating and bad breath.
- Pemphigus vegetans is the rarest form of the pemphigus complex.
In fact, there have been so few reported cases that it is difficult to
obtain information on breed, age, or sex associations; and on superior
treatment techniques. Pemphigus vegetans is thought by some to be a less
severe form of pemphigus vulgaris. Generally, the disease is limited to the
Clinical Signs: The clinical signs for pemphigus complex diseases vary
depending on the type of pemphigus the animal has. These differences have been
described to some extent in the preceding information. In general, the
affected areas are covered with pustules, crusts, and/or ulcerations of the
skin. Drainage of a clear to yellow/brown discharge and cracks in the affected
skin, deep enough to allow bleeding, are common. Secondary infections are
frequently seen. Itching (pruritus) is also extremely common with all forms of
pemphigus. Sometimes a coming and going progression of the disease is noted.
This can be accompanied by the sudden (hours to days) appearance of new
pustules in previously unaffected areas. This is followed by days to weeks of
crust formation over the previously affected areas.
Diagnosis: Diagnosing pemphigus complex autoimmune diseases is
generally made by a skin biopsy and histopathology. History and physical
examination provide extremely important information that is necessary in
helping to establish a diagnosis. Direct smears with special stains of the
crusts and skin discharge may also provide useful information in arriving at a
diagnosis of pemphigus foliaceous. Finally, there are special tests which may
be run by a laboratory specializing in skin samples. These tests include
immunofluorescence and immunohistochemical testing and can confirm a suspected
diagnosis of pemphigus complex disorder.
Treatment/Management: Treatment and management of the pemphigus complex
diseases are based on suppressing the immune system’s attack on the skin. In
doing so, it is important to establish a specific diagnosis of the type of
pemphigus. This is critical because the different pemphigus disorders have
different management techniques and vary on their response to treatment.
Pemphigus vulgaris, for example, is difficult to manage and is often fatal,
while pemphigus foliaceous is less severe, but may be fatal without treatment.
Pemphigus vegetans and pemphigus erythematosus are much easier to manage and
carry a good prognosis with treatment.
Therapy is usually initiated with large doses of corticosteroids (prednisone)
to induce remission of disease. Perhaps 40-50% of cases respond and may be
adequately managed on prednisone therapy alone.
In cases where management with corticosteroids alone is incomplete or
inappropriate, other drugs which suppress the immune system may be used.
Azathioprine may be used in dogs to help maintain pemphigus disorders in
remission. Frequently, a combination of both prednisone and azathioprine is
necessary to achieve and maintain remission in dogs affected with pemphigus.
Other medications which have been used include aurothioglucose, auranofin, and
chlorambucil. None of these drugs are particularly successful at
achieving remission, but seem to be effective at maintaining it. Doses of
immunosuppressive drugs needed to manage pemphigus complex diseases are
usually high, and it is important to consider the problems associated with
these treatments. Most animals will experience side effects, including a
weakened immune system, and may be more susceptible to infections. Boarding,
kenneling, grooming, and dog shows; or any other circumstance where the treated
dog will be exposed to other dogs, may need to be off-limits to help prevent
spreading of infections. Even exposure to a common upper respiratory virus in
an animal with a drug-induced weakened immune system may prove to be very
serious. It has been shown that exposure to sunlight tends to worsen many
cases of pemphigus complex, and the use of sunscreen lotion or avoiding the
sunlight altogether may help with therapy and management of these disorders.
- Lupus Diseases:
Introduction: Lupus erythematosus is a group of autoimmune diseases
where lymphocytes attack the body’s own tissues. Lymphocytes are a type of
white blood cell that normally help fight infection. Lymphocytes come in a
variety of types, each with a specific function in the immune system. In lupus
diseases, of which there are two major types in the dog, different lines of
these lymphocytes attack the body’s own tissues and produce disease. These
diseases are relatively uncommon in dogs.
- Systemic Lupus Erythematosus (SLE): This is an uncommon illness
where the lymphocytes attack a wide variety of tissues. Because of the
variety of tissues which may be attacked, the clinical signs associated with
this illness are also extremely varied and seem to mimic a number of other
diseases. SLE has been called "The Great Imitator" due to this
variety of signs/symptoms and the tendency to mimic other disorders. Among
the tissues that may be attacked is the skin. SLE may produce hair loss,
scale ("dandruff"), skin redness, itching, ulcerations, vesicle
(blister) formation, overgrowth of the footpads, and persistent secondary
bacterial infections of the skin. Any combination of these may be noted in
small areas of the skin or may affect the entire body. Areas not well
protected by hair such as the nose, lips, ears, armpit (axilla), groin
(inguinal area), abdomen, and portions of the limbs of some dogs are
Diagnosis: Diagnosing SLE is extremely difficult. There is no single
test which can specifically diagnose SLE. Tests which may be helpful in
establishing a diagnosis include bloodwork (CBC, serum chemistry profile)
and urine analysis. A test called ANA (anti-nuclear antibody) testing can
also be used in the diagnosis of SLE. It looks for immune system activity
against certain portions of the body’s own cells. Joint taps (if arthritis
is present) and skin biopsies (if skin disease is present) are also of
Treatment/Prognosis: Treating SLE is based on the body systems
affected. Generally, drugs which suppress the immune system are the key in
managing this disease. Corticosteroids, azathioprine, gold salts,
chlorambucil, cyclophosphamide, vincristine, levamisole, and aspirin have
all been used with varying degrees of success. Antibiotics for secondary
infections are commonly used. The prognosis is guarded– over 40% of dogs
die within a year of being diagnosed with SLE.
- Discoid Lupus Erythematosus (DLE): This is a more benign (and
more common) cousin of systemic lupus erythematosus. In DLE, lymphocytes
attack the nose and occasionally regions around the eyes, ears, limbs, lips,
and genitals. DLE is usually aggravated by exposure to sunlight and may
worsen in summer months. Breeds commonly affected by discoid lupus
erythematosus include collies, Australian shepherds, German shepherds,
Shetland sheepdogs, Siberian huskies, and other long-nosed breeds.
Clinical Signs: The clinical
signs of DLE begin on the nose. Often, the loss of the rough,
"cobblestone" appearance of the nose and its replacement with a
smooth surface is a very early clinical sign of discoid lupus erythematosus.
Loss of the dark pigment usually found in the nose area is also common, with
the tissues taking on a pink, inflamed, and crusted look. Minor cases may
never progress beyond these early clinical signs. Severe cases advance to
involve the entire nose, sometimes with destruction of the supporting
cartilage. This results in an unsightly and very painful situation. Even in
the more severe cases, the dog may appear otherwise healthy and normal.
Rarely, a malignant and dangerous type of cancer known as squamous cell
carcinoma has been known to develop from the chronically irritated skin and
nasal tissues of DLE. In most cases where squamous cell carcinoma has
developed, the DLE had been a problem for years, and no protection from
sunlight had been used.
Diagnosis: Diagnosing DLE is
based on history, clinical signs, physical examination, and skin biopsy. A
biopsy is necessary for a positive diagnosis and is generally very well
tolerated with a quick recovery.
Treatment/Prognosis: Therapy differs according to how severe an
individual case may be. Minor cases may benefit greatly by reduced
exposure to sunlight and/or the use of topical treatments such as sun screen
and corticosteroids. Moderate to severe cases may require more aggressive
therapy. Corticosteroids, vitamin E, sun screen, and fatty acids have all been
used. A combination of niacinamide and tetracycline, two relatively safe and
inexpensive medications, has shown great promise in many cases, but may take
as long as 2-3 months to produce results. Except for the rare squamous cell
carcinoma development, the prognosis is generally very good. Lifelong therapy
is required in most cases to keep DLE under control.
- Erythema Multiforme:
Introduction/Causative Agents: Erythema multiforme is an uncommon
autoimmune illness of the skin which affects dogs. It is thought that this
condition represents a sudden attack by the immune system on skin tissue that
is brought on by certain triggers. The most common triggers thought to lead to
erythema multiforme are drug reactions and skin infections. A variety of drugs
have been associated with this problem, including some of the common
antibiotics used in canine medicine.
Clinical Signs: Erythema multiforme begins with symmetrical red
patterns which may progress to blister-like areas and eventually to tissue
death and sloughing. Body areas commonly affected by this condition include
the abdomen, axillae (armpit areas), inguinal (groin) area, lips, mouth, ears,
footpads, and region around the eyes.
Diagnosis: Diagnosing this disease is based on history, physical
examination, clinical signs, and skin biopsy.
Treatment: Treatment of erythema multiforme focuses on correcting any
underlying cause. If the underlying cause is removed, the condition itself
usually resolves within a few weeks without any specific treatment. Severe
cases have been treated successfully with drugs that suppress the immune
system (corticosteroids and cyclosporine).
Neoplastic (Tumors and Cancer) Skin Problems
Introduction: Skin tumors and cancers are very common in dogs and the
list of tumor types and cancers is long. Some grow slowly as single or solitary
lumps and do not tend to spread beyond the immediate tumor area. Others may grow
quickly, involve large or multiple areas of the skin, and may spread to internal
organs causing a life-threatening situation. Tumors can be benign (less
invasive, less destructive) or malignant (invasive, destructive, and may spread
to other locations).
Identification of the tumor type or class is extremely important when facing
a possible skin cancer situation. There is no way to predict what any tumor will
do or how serious a skin lump may be without a specific diagnosis.
Diagnosis: The diagnosis of skin
tumors or lumps is based primarily on biopsy or removal of the tumor and
subsequent histopathology. Some are possible to diagnose with a fine needle
aspirate and cytology. This does not require anesthesia, but a specific
diagnosis is usually not possible with this technique.
Treatment: Treatment of skin tumors
and malignant cancer types varies with the specific tumor. Removal of the tumor
is usually at the top of the list of treatment recommendations. In many cases,
removal of the tumor cures the dog. Tumor removal techniques vary a great deal
and range from a simple snip excision to amputation of an entire limb. Other
treatment recommendations may include radiation therapy, chemotherapy,
hyperthermia (heat therapy), and cryotherapy (freeze-burning). Nutritional
cancer therapy is a field which has received much attention in the last decade,
and prescription diets are commercially available through veterinary hospitals
which appear to have benefit in slowing the growth of many types of cancer.
See the information on page E495 for additional details on the diagnosis and
treatment of tumors in general.
The following list of tumors and skin cancer types is not meant to cover all
the possible skin tumors, but will include many of those most common in the
canine patient. The purpose is to give dog owners a brief description of the
tumor or skin cancer type after a diagnosis has been made. This list is
not intended to provide the diagnosis of a lump or tumor. These tumors and
cancers are listed in order of how frequently they are diagnosed in dogs living
in the United States.
Mast Cell Tumor:
Introduction: Mast cell tumors (MCTs) are the most common skin tumor
in the dog. The average age at diagnosis is 9 years old, although a mast cell
tumor has been seen in a 3 month old puppy. Breeds at risk include mixed breed
dogs, boxers, Boston terriers, beagles, schnauzers, Labrador retrievers,
weimaraners, dachshunds, golden retrievers, pugs, and shar peis.
Clinical Signs: Mast cell tumors of the skin may appear as distinct lumps
or as varying sized patches of lumpy skin. They may be slow or fast-growing.
Mast cell tumors have the potential to spread internally and cause
life-threatening disease. Therefore, it is not a tumor type to be treated
lightly. The location of the tumor on the body can indicate how serious the
problem might be. The outcome tends to be worse if the tumor is located in the
mouth, near the anus, around the prepuce, or in the nail beds.
Diagnosis/Treatment: This is one of few tumor types which can be
diagnosed with a fine needle aspirate and cytology. Treatment depends on the
location and grade (a score given to MCTs based on histopathology which can
strongly predict the outcome) of the tumor. A veterinary oncologist (cancer
specialist) may become involved in difficult cases.
Introduction: Perianal adenomas or circumanal gland tumors are very
common in male dogs. While they can occur in female dogs, they are far less
common. Breeds at risk include dachshunds, German shepherds, beagles, shih tzus,
cocker spaniels, English bulldogs, Samoyeds, Lhasa apsos, and Siberian huskies.
Clinical Signs: These tumors are usually small, round, nonpainful,
slow-growing lumps located on the hairless skin around the anus. They may be
solitary or multiple in number. Usually perianal adenomas are benign and do not
cause any problems; however, if the tumor is malignant, it can cause
life-threatening illness by spreading to other areas.
Diagnosis/Treatment: A diagnosis must be made by histopathology– it is
very difficult to tell the difference between benign and malignant perianal
gland tumors with cytology alone. Treatment for the common benign variety may be
accomplished with tumor removal or cryosurgery. Castration of intact male dogs
is also helpful. Treatment for the malignant type involves aggressive removal
and potentially radiation and/or chemotherapy. Multiple surgeries may be
necessary for some cases. Malignant circumanal gland tumors in some dogs
(especially females) can be incurable, leading to death in some cases.
Introduction/Clinical Signs: Lipomas or fatty tumors are common in dogs
and usually occur in dogs older than 8 years of age. They are benign
growths, originating from fat cells (adipocytes). They are most common on the
thorax, abdomen, and front legs. Breeds at risk include cocker spaniels,
weimaraners, Labrador retrievers, dachshunds, Doberman pinschers, miniature
schnauzers, and small terriers.
Diagnosis/Treatment: Lipomas can be best diagnosed by histopathology.
Cytology can be a useful diagnostic tool as well; however, many tumors contain
fat cells, and cytology alone may lead to an incorrect diagnosis of a lipoma. The
ideal treatment for lipomas is surgical removal of the tumor. In overweight
animals, a restricted diet for some weeks prior to surgery may help reduce the
size of the lipoma and improve the surgeons ability to distinguish the tumor
from surrounding tissues. This will greatly reduce surgery time and increase the
chances of completely removing the tumor.
Sebaceous Gland Tumors:
Introduction: Sebaceous glands are found throughout the skin,
especially in areas that require moist and pliable skin, such as the
eyelids and lips. They are also found in between foot pads, on the chin, and on
the tail, where they may have scent-marking functions. Sebaceous glands produce
an oily substance that keeps skin moist and healthy. Tumors of these glands are
common, most often occurring in dogs 9 years of age and older. Breeds at risk
include cocker spaniels, dachshunds, Irish setters, miniature schnauzers,
beagles, Siberian huskies, poodles, shih tzus, Lhasa apsos, and malamutes.
Clinical Signs/Diagnosis: There are several types of sebaceous gland
tumors, most of which are benign. These tumors often appear as white to pink,
raised, cauliflower-like growths commonly occurring on the limbs, head, trunk,
and eyelids. Diagnosis is by histopathology, although clinical appearance and
cytology may also establish a fairly accurate diagnosis.
Treatment: Proper treatment may include surgical removal, cryotherapy,
or observation without treatment. Malignant sebaceous gland tumors do occur and
should be removed surgically as soon as possible. However, these malignant
tumors rarely spread beyond the original tumor area.
Introduction/Clinical Signs: Fibrosarcomas are aggressive, malignant
tumors that occur anywhere on the body, but more commonly on the limbs and the
trunk. Golden retrievers, Doberman pinschers, and cocker spaniels are breeds at
risk. Fibrosarcomas are usually irregular, firm, sometimes lumpy growths that often do not have distinct borders. They generally grow rapidly and may ulcerate
and drain at the surface.
Diagnosis/Treatment: Diagnosis is accomplished by histopathology.
Cytology may help identify the typical spindle-shaped cancer cells which make up
fibrosarcomas, but large areas of hemorrhage and tissue death commonly found
inside the tumors may yield confusing cytology results. Treatment begins with
aggressive surgical removal. Radiation therapy, chemotherapy, and cryotherapy
may be helpful in some cases.
Introduction/Clinical Signs: Melanomas are tumors arising from
pigmented cells and are usually found as black, gray, or brown growths. They
occur most commonly on the head, limbs, toes, scrotum, lips, mouth, thorax, and
abdomen. Breeds at risk include schnauzers, Airedale terriers, Boston terriers,
Scottish terriers, boxers, Chihuahuas, chows, springer spaniels, cocker
spaniels, Doberman pinschers, golden retrievers, and Irish setters.
Melanomas may occur as benign or malignant growths. Malignant melanomas are
tumors with a risk of spreading and causing aggressive destruction of internal
organs. This is especially true if the tumor originates in the mouth or nail
Diagnosis/Treatment: Histopathology is the primary method of diagnosis.
Aggressive surgical removal of the tumor is the treatment of choice, although
spreading of the tumor may already have occurred at the time of diagnosis. The
average survival time in one group of dogs with melanomas located inside the
mouth was 3 months following surgical removal. Radiation therapy and
chemotherapy have been used with varying success.
Introduction: Histiocytomas are common benign tumors which tend to occur
in young dogs. Breeds at risk include boxers, dachshunds, cocker spaniels,
rottweilers, Great Danes, schnauzers, shar peis, Boston terriers, Shetland
sheepdogs, Labrador retrievers, and Doberman pinschers.
These are solitary, firm, round or disk-shaped and tend to occur on the head,
limbs, and ears. They frequently ulcerate at the surface and may grow
surprisingly rapidly for a benign tumor. Occasionally, this tumor type may occur
in groups and may even spread to lymph nodes– this type of histiocytoma is
probably more common in shar peis.
A diagnosis is made based on histopathology. Because of its rapid rate of growth
that is not typical of benign tumors, histiocytomas often appear as malignant
cancer. It is usually a great relief to have a report of histiocytoma come back
from a pathologist after the cytology seemed to indicate a malignancy.
The majority of histiocytomas recede on their own within a few months. Surgical
removal is curative, and cryotherapy has also been successful at treating
histiocytomas. In cases where surgical removal is difficult due to location on
the body, but the tumor is causing discomfort or has become infected, the use of
a topical corticosteroid with dimethyl sulfoxide (DMSO— a powerful medication
which helps other drugs cross skin barriers they otherwise would not) has been
Squamous Cell Carcinoma:
Introduction/Causative Agents: Squamous cell carcinoma (SCC) is probably
the condition most frequently associated with the term "skin cancer."
SCC arises from the most superficial layer of skin and is associated with
exposure to excessive sunlight, virus infections of the skin, radiation, burn
and frostbite scars, and chronic skin irritation. Unmanaged discoid lupus
erythematosus of the nose may also develop into SCC.
Breeds at risk include Scottish terriers, Pekingese, boxers, poodles, and
Clinical Signs: One form of squamous cell carcinoma affects the nail
beds and causes a painful swelling of the toe. This form more commonly affects a
different set of dog breeds. These are usually large breed dogs with black coats such as Labrador retrievers, Bouvier de Flandres, standard poodles, and
giant schnauzers. Sunlight-induced squamous cell carcinoma occurs in breeds with
short, white hair coats such as dalmations, beagles, and bull terriers. SCC can
occur on the trunk, limbs, toes, scrotum, lips, anus, and nose. Skin in which
squamous cell carcinoma arises may appear as an open sore or wound that does not
heal, or may occur as cauliflower-like nodules of varying size. Toes which are
affected may be swollen, painful, and have the toenail fall off. SCC is a locally
aggressive malignant cancer. This means that surrounding tissues are often
damaged and destroyed. Lymph nodes may be affected locally in some cases.
Diagnosis/Treatment: Histopathology is necessary for a diagnosis.
Radiographs of SCC of the toe are helpful because they may identify if bone is
affected and if the swelling is more than an infection of the soft tissues.
Treatment of SCC may include surgical removal of the cancer, cryotherapy,
hyperthermia, or radiation therapy. Amputation of a toe affected with SCC will
usually cure the cancer, although the amputation may need to be aggressive, with
the location of the amputation one knuckle joint above any affected tissue.
Amputation of the affected portion of the nose ("nosectomy") is
required in SCC resulting from unmanaged discoid lupus erythematosus. The
cosmetic result is often surprisingly acceptable, and the surgery will usually
cure the problem. In all cases, it is important to avoid additional exposure to
sunlight. This is critical because new squamous cell carcinoma development is
common in dogs that have already been diagnosed with the disease if ultraviolet
light is not avoided.
Introduction/Clinical Signs: Hemangiopericytomas are skin tumors which
occur frequently in older dogs on the limbs, especially the knee (stifle) and
elbow joints. They tend to be firm, lumpy, raised masses of varying sizes.
Breeds at risk include boxers, German shepherds, cocker spaniels, beagles, Irish
setters, springer spaniels, Siberian huskies, and collies. Hemangiopericytomas
rarely spread to other areas of the body. They may be difficult to completely
cure because they can recur following surgery. With each recurrence of a
hemangiopericytoma, they appear more aggressive and become even more difficult
to cure. The longer a hemangiopericytoma has been present prior to surgery, the
more likely it is to recur.
Diagnosis/Treatment: Histopathology is the diagnostic test of choice for
diagnosis. Treatment is accomplished by surgical removal and/or amputation of
the affected limb. Radiation therapy has also been somewhat effective in certain
- Basal Cell Carcinoma:
Introduction: Basal cell carcinomas are a large class of tumors arising
from skin and a few other tissues. These tumors are associated with exposure
to ultraviolet light in people, but this correlation has not been proven in
Clinical Signs: These tumors are usually slow-growing, firm, rounded,
and may ulcerate on the surface. Basal cell carcinomas are also frequently
pigmented and may have the appearance of a melanoma. While the term
"carcinoma" implies a malignant growth, basal cell carcinomas are
considered to have a low grade of malignancy and rarely spread beyond the
Diagnosis/Treatment: Histopathology will identify this type of
tumor. Treatment may be achieved by surgical removal of the tumor or
Introduction/Clinical Signs: Papillomas or warts are common in dogs
and occur in a variety of ways. Cauliflower-like pink to white multiple or
solitary lumps may occur on the head, eyelids, feet, abdomen, groin, and
mouth. This tumor type results from skin infections of papillomaviruses.
Breeds at risk include schnauzers, cocker spaniels, kerry blue terriers, and
shar peis. A rather severe form of this problem is known as canine oral
papillomatosis. Papillomatosis causes the mouth and throat tissues of young
dogs to become covered with white, cauliflower-like masses. This form of
papillomas does not appear to have any breed preferences and can affect any
dog. Papillomavirus infection of the skin has also been associated with the
development of squamous cell carcinoma.
Diagnosis/Treatment: Histopathology is the diagnostic tool most
often utilized to establish a certain diagnosis; however, papillomas are often
diagnosed visually upon close inspection. Treatment of papillomas can include
surgical removal, cryotherapy, and observation (no treatment). Canine oral
papillomatosis usually resolves on its own within 3-4 months. Use of retinoids
or interferon therapy may help improve recovery times.
Introduction/Clinical Signs: Hemangiomas of the skin are benign tumors
arising from the lining of small blood vessels. These tumors appear as well
defined, rounded, blue-black to red masses of varying firmness and size.
Hemangiosarcoma is the malignant and, fortunately, less common cousin of the
hemangioma. Hemangiosarcomas appear as blue-black to red masses, often with a
bruised appearance. They tend to be closely associated with surrounding normal
tissue and may grow to be incredibly large. Breeds at risk include boxers,
golden retrievers, German shepherds, dalmations, beagles, springer spaniels,
Bernese mountain dogs, basset hounds and pointers. Long term exposure to
sunlight may lead to hemangioma and hemangiosarcoma formation in the
sparsely-haired areas of light-skinned dogs. Hemangiosarcomas may arise from
internal organs, especially from the liver and spleen, and then spread to the
skin; therefore, it is important to fully research the possibility of internal
original tumors when a skin hemangiosarcoma is diagnosed.
Treatment: Aggressive surgical removal is considered the therapy of
choice; however, the prognosis for dogs with hemangiosarcoma is usually poor
because the cancer is extremely aggressive and spreads quickly to other
tissues. Chemotherapy has also been used as a treatment option with some
Introduction: Lymphoma is a malignant cancer of the lymphocytes.
(Lymphocytes are cells that are important to the immune system in fighting
infection.) Any tissue with lymphocytes can be affected, including the skin.
There are several classes of lymphoma, including a condition known as
"mycosis fungoides." Many years ago a skin condition unlike most
types of cancer was originally thought to be a fungal infection. This
condition has since been shown to be lymphoma in a form which appears much
like immune-mediated skin disease or a skin infection. The name "mycosis
fungoides" has never been changed, although it is misleading because it
implies a fungal infection.
Clinical Signs: Lymphoma can appear as solitary or multiple skin
masses or plaques and may affect nearly any part of the skin. The nose, mouth,
footpads, genital areas, anus, and any haired or non-haired area of skin may
be involved. Mycosis fungoides can appear as reddened, itchy, scaly skin
across large areas of the body. It can also appear as ulcerations, crusting,
swelling, irritation, and loss of pigment around the nose, eyes, and lips,
much like pemphigus complex.
Diagnosis/Treatment: The diagnosis of lymphoma is made by biopsy and
histopathology of affected areas. Prognosis for dogs with lymphoma of the skin
is poor and is considered grave for dogs with the mycosis fungoides form.
Surgical removal of the cancer in these cases is not possible because such
extensive areas of the body are usually involved. Chemotherapy and different
combinations of drugs are sometimes successful. For mycosis fungoides, topical
application of nitrogen mustard (mechlorethamine) is used successfully in
treating the irritated skin part of this disease. Even though most dogs
experience an improvement in the clinical signs, there is no evidence that
this therapy extends the lifespan of a dog diagnosed with mycosis fungoides.
Retinoid therapy has been used, but with unpredictable success.
Endocrine-Related Skin Disorders
Introduction: These are skin
abnormalities caused by problems with the organs that excrete hormones and
related substances. These disorders are encountered on a relatively regular
basis in dogs. Three of the most common endocrine diseases affecting the skin
will be discussed:
Introduction/Clinical Signs: Hypothyroidism is the most common
endocrine disease seen in dogs affecting the skin. Signs of skin disease tend
to develop slowly over several months. Initially, alopecia (hair loss) is
usually seen over the animal’s trunk, tail (giving a "rat tail"
appearance), thighs, or flanks. In time, the alopecia worsens, becoming
symmetrical, but tends to spare the head and limbs. Hair often fails to regrow
after clipping or shaving. The hair coat in general tends to appear dull, dry,
and brittle. Scale (dandruff), increased skin pigmentation, and thickened skin
are common. Secondary bacterial, parasitic (mites), or fungal (yeast) skin
infections are also very common. If pruritus (itching) is present, it is
primarily due to the secondary infections.
Diagnosis/Treatment: The general diagnosis and treatment of
hypothyroidism is discussed elsewhere (see page F815). The skin disorders
related to hypothyroidism do respond to treatment. Once treatment is started,
the skin problems tend to worsen before showing signs of improvement.
Significant hair regrowth can be seen within 4-6 weeks of beginning treatment,
although it may take 4-6 months for hair regrowth to be complete.
Introduction/Clinical Signs: Hyperadrenocorticism or Cushing’s
disease may occur naturally or may be iatrogenic (caused by people) because of
long-term use of glucocorticoid therapy. Skin changes may begin as an
unhealthy appearance of the hair coat. Owners may find that grooming
appointments are not needed as frequently because the hair is not growing as
fast as it normally does. The coat may change color early on, with black and
brown hairs lightening to rust or tan. Hair is eventually lost, leading to
symmetrical hair loss over the trunk. The skin tends to become thin and
wrinkled, heals slowly from cuts and scrapes, and bruises easily. Secondary
skin infections (bacterial, fungal, parasitic) are common.
Diagnosis/Treatment: Skin disorders related to Cushing’s disease
respond variably to treatment. Improvement is usually noted, but may not be
complete even in well-managed dogs. See page F138 for an in-depth discussion
of Cushing’s disease including diagnosis and treatment.
- Diabetes mellitus: While skin-related problems due to diabetes occur
only in a minority of cases, diabetes is a relatively common disorder in dogs.
When skin disease does occur in association with diabetes, secondary skin
infections are the biggest problem. Varying degrees of hair loss, scale
(dandruff), and thin skin may also be noted. These abnormalities may or may
not be correctable through the proper treatment of diabetes. See page F153 for
additional details on diabetes.
Miscellaneous Skin Disorders
Introduction: The term "seborrhea" is used to describe a
defect in either production of sebum (normal skin oils) or keratinization
(normal growth and turnover of skin cells), or a combination of both.
Abnormalities can occur with both quality and quantity of sebum. Generally,
seborrhea is a secondary condition seen in association with an underlying
primary cause such as allergic skin disease or endocrine-related skin
disorders. Primary seborrhea does occur, but it is uncommon.
Types of seborrhea:
- Seborrhea sicca: Seborrhea sicca is thought to be a result of
decreased sebum/oil production leading to dry, dehydrated skin. The hair coat
is dull and the skin is dry with "scale" (white or gray flakes of
dry skin found in hair coat). Seborrhea sicca is the most common form of
seborrhea seen in dogs.
- Seborrhea oleosa: With this problem, excessive sebum/oil
production in the skin causes a thick, greasy, sticky hair coat. This
condition is usually very messy and can emit a foul odor.
- Combination seborrhea sicca/oleosa: The hair coat appears dull
like seborrhea sicca, but feels greasy like seborrhea oleosa. This is probably
due to increased production of a poor quality sebum. The increased quantity of
sebum creates the greasy feel to the hair coat, but the abnormal quality of
sebum still allows drying of the skin.
Treatment: The treatment of seborrhea focuses on treating or correcting
the underlying cause. Moisturizing shampoos/conditioners that contain
sulfur/salicylic acid are extremely helpful with seborrhea sicca (see page G750). Seborrhea oleosa can be managed with a de-greasing shampoo/conditioner
that contains benzoyl peroxide or coal tar (see page G659).
Nutritional Skin Disorders:
Introduction: A number of nutritional deficiencies or excesses can lead
to skin disease. Notably among these are deficiencies of vitamins A, B, and E,
fatty acids, protein, and zinc; or excessive levels of vitamin A.
- Vitamin A: Vitamin A is stored very well in the body. Because of
this, excesses of vitamin A are probably more of a concern than is vitamin A
deficiency. Both vitamin A deficiencies and excesses cause similar skin
problems. Poor hair coat, scaling (seborrhea sicca), hair loss, and
secondary skin infections are commonly seen. One major difference between
cases of vitamin A deficiency and vitamin A excess is that pain is sometimes
noted during the physical exam of a patient with vitamin A toxicity. This is
due to bone changes in the spine. Vitamin A can be given as a single
injection or with low-dose oral therapy. Oral therapy tends to be expensive,
but sometimes necessary for certain cases.
- Vitamin B: Vitamin B deficiencies often cause seborrhea sicca with
varying degrees of hair loss. Vitamin B is manufactured by bacteria found in
the intestine and is constantly absorbed over time. It is not stored in the
body, so vitamin B excesses do not occur. Any disease affecting the
intestine’s ability to absorb nutrients or affecting the population of
bacteria found in the intestine has the potential to result in vitamin B
deficiency. Because it affects the bacteria found in the digestive tract,
prolonged antibiotic therapy may also result in a vitamin B deficiency.
Supplementation with vitamin B products in any dog with chronic seborrhea
failing to respond to therapy may be very helpful.
- Fatty acids: Fatty acid deficiency may be seen in dogs fed only
dry, commercial foods that have been improperly preserved or stored. It can
also be seen in dogs fed homemade diets. Skin disorders resulting from fatty
acid deficiency are seen several months after starting the diet. Fatty acid
deficiency leads to skin thickening, seborrhea sicca, seborrhea oleosa, hair
loss, and secondary skin infections. Supplementation with essential fatty
acid capsules or household oils (i.e. corn oil, sunflower oil, or canola
oil) may correct the problem, but it is generally better to upgrade the diet
to one of higher quality. Sometimes, fatty acids are withheld purposely for
certain medical conditions such as pancreatitis and obesity. In these cases,
the seborrhea and skin infections may have to be treated without correcting
the fatty acid deficiency.
- Vitamin E: Naturally occurring vitamin E deficiency is rare in
dogs. Some cats fed exclusively high-fat diets do suffer from vitamin E
deficiency, and the same is theoretically possible for dogs. Some laboratory
dogs have been experimentally made to suffer from vitamin E deficiency.
These dogs showed signs of seborrhea (seborrhea sicca at first, followed by
seborrhea oleosa) and inflamed, itchy skin. They responded dramatically to
oral vitamin E supplementation. Topical vitamin E oils are frequently used
in a variety of skin diseases in dogs, sometimes with surprising success.
- Protein deficiency is unusual because most dog foods now
available contain adequate or even high protein levels. However, some diets
may be low in protein in order to treat another condition such as kidney
failure. Homemade vegetarian diets may also lead to protein deficiency in
dogs. Protein deficiency leads to color changes in the hair coat (lightening
of darker hair), skin thickening, hyperpigmentation (darkening) of skin, and
patchy hair loss. The coat is brittle, dry, and rough. The changes are
usually symmetrical over the trunk, legs, head, and feet. Supplementation
with protein generally provides a good response.
- Zinc-responsive dermatosis: There are two types of zinc-responsive
dermatosis syndromes seen in certain dog breeds. The first type (Syndrome I)
occurs in Siberian huskies, Alaskan malamutes, and sometimes in Bull
terriers. Skin disease usually begins to occur by age 3 and appears as
crusting, redness, and swelling with drainage around the eyes, mouth, chin,
and ears. Genital areas may be occasionally affected. The condition seems to
develop regardless of diet, which is why the disease is not referred to as a
zinc deficiency. Because the disease is probably inheritable, it is
not recommended that affected dogs be bred.
The second type (Syndrome II) occurs in quickly growing puppies fed diets
low in zinc or diets oversupplemented with other vitamins and minerals that interfere with zinc absorption. Inflamed callouses tend to form over bony
areas, with deep crevasses and drainage. Secondary infections may occur, and
lymph nodes may become enlarged and painful.
Zinc levels can be measured in hair or blood, but are not very reliable.
Treatment consists of supplementing the diet with zinc sulfate, zinc
methionine, or zinc gluconate. In Syndrome II, once the skin appears normal
again and the dietary cause of the problem has been corrected, zinc
supplementation may be stopped. Zinc supplementation is usually lifelong for
Syndrome I. Some Siberian huskies do not respond to oral zinc therapy and
must receive periodic zinc-containing injections.