Canine Skin Disorders

Skin diseases are common in dogs. Although seldom fatal, many are chronic. They can be controlled but not cured. Therefore, many skin diseases require frequent, if not lifelong, treatment.

Because there are many causes of skin diseases in dogs, diagnosis is often difficult and response to treatment may take time to evaluate. Many diseases cause similar clinical signs, making diagnosis even more difficult.

Bacterial, fungal, allergic, parasitic and hormonal skin diseases occur in dogs. Less commonly, hereditary and immune-mediated forms of skin disease also affect dogs. Many skin diseases cause intense itching which can lead to further skin damage from self-mutilation. Skin tumors and cysts are common in older dogs.





Causes -- Staphylococci (‘Staph bacteria’) are the most common organisms found in bacterial skin diseases (pyodermas) in dogs.

Signs -- Itchy, yellow pustules are often observed early in the disease, and the dog’s skin can be reddened and ulcerated. Dry, crusted areas appear as the condition advances, along with loss of hair in the affected areas and an odor.

All areas of a dog’s body may be involved, but most cases are confined to the trunk. The chin is one area commonly affected. Called chin acne, this condition is actually a deep bacterial infection. Obese dogs and brachycephalic breeds are frequently affected by pyoderma in the skin folds on their face, lips and vulva. Pyoderma can also occur between the toes, on elbow calluses, and in the abdominal area in young puppies.

Diagnosis -- Determined by medical history & appearance and location of the lesions. It may be necessary to culture the skin and conduct sensitivity tests to determine which antibiotic will be effective in treatment. Most bacterial skin infections in dogs are secondary to other diseases such as parasitism, allergies, endocrine (hormonal) disorders or abnormalities in the immune system. Therefore, in recurrent cases, it is important to search for underlying causes. It may be necessary to do blood tests, allergy tests or skin biopsies to achieve a complete diagnosis.

Treatment -- Initial treatments may involve shaving around the lesions, cleansing the affected area with an antibiotic shampoo, and the application of an antibiotic ointment to local lesions. In most cases, antibiotics will also be administered orally for 3-4 weeks. Bandages or a protective collar which prevent the dog from coming in contact with the lesions may be necessary.

It may be necessary to continue treatments such as medicated shampooing, antibiotic ointment applications and giving antibiotics orally at home. While most cases respond to treatment, recurrences of pyoderma are common, particularly if treatment recommendations and follow-up visits to your veterinarian are not followed to completion.

Cause -- The fungal skin infections of dogs are caused primarily be two species of fungi: Microsporum and Trichophyton. The skin diseases resulting from these fungi are commonly called ‘ringworm.’

Signs -- Ringworm is seen most commonly in young dogs. The fungi live in dead skin tissues, hair and nails. Hair loss, usually in circular patches, may appear. If infected, the center of the patches may have a dry, crusty appearance. The head and legs are most commonly affected by ringworm, although the disease may spread over other parts of the dog’s body if not treated.

Diagnosis -- The appearance of the lesions, the history of their development and the age of the dog are all helpful in diagnosing ringworm. A Wood’s Lamp Test (ultraviolet light) can be used to help diagnose the Microsporum species. A definite diagnosis can be obtained through a fungal culture (growth of the fungi found on the affected hair in a culture medium).

Treatment -- The hair around the lesions is clipped and medicated fungicidal shampoos can be used for bathing the dog. Topical lime sulfur solution and systemic medications should be administered.

Public Health Aspects of Ringworm -- Ringworm is contagious to humans, particularly to children and to other household pets. Infected dogs should be kept away from children and other dogs and cats until the infection has resolved, which can be as long as 2-3 months after the treatment begins. Adults should be careful to wash their hands thoroughly after handling a pet diagnosed with ringworm. If treated early, ringworm is readily controlled in humans. Other household pets should also be examined for ringworm.

Allergies in dogs are common. Signs such as itchy skin, nasal and eye discharge and sneezing, and/or digestive upset and/or skin lesions may indicate an allergy is present. Many skin diseases seen in dogs are caused by an allergy.

Causes -- An allergy is a hypersensitivity reaction to allergy-causing substances known as ‘allergens’or ‘antigens.’ Dogs (like people) can develop allergies at any age, and the signs can appear quite suddenly.

The most common allergy dogs develop is an allergy to flea saliva. The presence of a single flea on these allergic dogs causes intense itching and scratching. These allergies are seasonal in climate zones where fleas are eliminated by the cold in winter months, and a year-round problem in warmer climates.

Atopy (atopic dermatitis, allergic inhalant dermatitis) is a pruritic (itchy) skin disease dogs develop in response to inhaled particles such as house dust, molds and pollens. This common form of allergy usually starts at a relatively young age. Dogs can also be allergic to chemicals contained in soaps, waxes, carpets cleaner, and other household products. This type of hypersensitivity is known as a ‘contact allergy.’ Also, many dogs are allergic to insect bites and stings. Pets can also have food allergies, which usually result in gastrointestinal upset and/or skin lesions.

Signs -- Itching is the primary sign of allergic skin diseases in dogs. The affected skin may appear red and moist in patches called ‘hot spots.’ Pus and dried crusty material are apparent if a bacterial infection is also present. The dog tends to frequently scratch, lick, and/or bite affected areas. Flea allergies are most evident over the dog’s back and near the tail. A dog’s face, feet, chest, and abdomen are more often affected by pollen and dust-type allergies. Contact allergies are seen mostly on the hairless areas of the abdomen and on the bottoms of the feet.

Diagnosis -- The dog’s medical history is essential to determining the diagnosis. The intense itching and location of the lesions are also helpful in determining the type of allergy present. Response to treatment (flea control) is often used as a method of diagnosis of flea allergy. Trials of special hypoallergenic diets are used to diagnose food allergy. Allergy testing is used to help choose immunotherapy. Ask your veterinarian for his current recommendations.

Treatment -- Allergies can be controlled in most cases. There are very few cures. Antihistamines and corticosteroids may be used by your veterinarian to give your dog relief from the intense itching. In most cases this will stop the intense itching and scratching. The main objective in controlling flea allergies in dogs is to kill the fleas on the dog and in the dog’s environment.

Another approach to allergy control is hyposensitization (immunotherapy). In this procedure, a correct diagnosis by intradermal or blood testing is necessary. The dog is then given injections of small but increasing doses of the allergy-causing substance at varying intervals for up to 12 months. Lifelong response may take up to 12 months.

Cause -- Fleas are the most common parasitic skin disease found in dogs. Mange is another type of skin disease which is caused by mites. There are two severe types of mange: sarcoptic mange and demodectic mange. Ear mites, lice, and ticks are other parasites that affect dogs. Their presence irritates the dog’s skin and causes self-mutilation.

Signs -- Sarcoptic mange causes intense itching, loss of hair and crusting of the skin. A dog’s ears, front legs, chest and abdomen are most often affected by sarcoptic mange.

Demodectic mange can cause itching. The skin is reddened and scaly, and hair loss occurs in round patches resembling ‘ringworm.’ The face and front legs are most commonly affected, although some cases may be generalized. Generalized demodectic mange is often a sign of underlying internal disease or a hereditary problem.

Ear mites cause severe irritation in the ears. Often, an affected dog will scratch the hair off the back of its ears. Ticks, lice and fleas may transmit other diseases, in addition to causing irritation.

Diagnosis -- Mange is often suspected on the basis of the medical history and the appearance and location of the lesions. A skin scraping test is done to aid in identifying parasites. Ear mites, which are barely visible to the naked eye, appear as small white objects. The black debris commonly seen in the ears of dogs with ear mites is a combination of dried blood, normal ear wax and discharge from inflammation. Lice, fleas and ticks can also be seen by close examination of the dog’s skin.

Treatment -- Mange is treated by clipping the affected areas and washing them with an antiseptic. Medicated shampoos or dips are often necessary and may be used weekly or biweekly for several months. Most cases of mange respond well to this treatment. Antibiotics can be administered in cases of mange where infection may be present.

Ear mites can be readily treated. The animal’s ears need to be thoroughly cleaned. Then, a topical ear mite solution can be applied to the inside of the ear. There are single treatment applications which kill ear mites (Acarexx). The ears should be checked for mites with a magnified otoscope a few weeks after treatment to determine if another medicated application is necessary.

Skin diseases caused by hormonal abnormalities in dogs can be difficult to diagnose. The thyroid gland, adrenal glands, pituitary gland, testicles and ovaries all produce hormones. If excessive (‘hyper’) or deficient (‘hypo’), these hormones produce changes in the skin and hair coat. Most hormonal problems that affect the skin produce hair loss that is evenly distributed on each side of the dog’s body. The skin may be thicker or thinner than normal, and there may be changes in the color of the skin or hair coat. Hormonal skin diseases are usually not itchy.

When any of the hormone-producing glands malfunction, they affect other body functions besides the skin. Hormonal skin diseases in dogs can be much more serious than just a ‘skin problem.’ Some causes of hormonal skin disease, such as hypothyroidism and adrenal gland problems, can be diagnosed by special blood tests and effectively treated. Others may be more difficult to diagnose and treat. Skin changes related to the sex hormones can be successfully treated with surgical neutering, if this has not been performed previously.

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