Dog skin disorders are among the most common health problems in dogs. Skin disorders in dogs have many causes, and many of the common skin disorders that afflict people have a counterpart in dogs. The condition of dog's skin and coat can also be an important indicator of its general health. Skin disorders of dogs vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. They also need to be differentiated on the basis of being of primary or secondary (due to scratching, itch) in nature, making diagnosis complicated. Dog skin disorders may be grouped into categories according to the causes.
Skin disease may result from deficiency or overactivity of immune responses. In cases where there is insufficient immune responses the disease is usually described by the secondary disease that results. Examples include increased susceptibility to demodectic mange and recurrent skin infections, such as Malassezia infection or bacterial infections. Increased, but harmful immune responses, can be divided into hypersensitivity disorders such as atopic dermatitis, and autoimmune disorders (autoimmunity), such as pemphigus and discoid lupus erythematosus.
Canine Atopic Dermatitis
Canine atopy is a hereditary and chronic allergic skin disease. It usually starts between 6 months and 3 years of age with some breeds of dog such as the Golden Retriever starting at an earlier age. Dogs with AD are itchy, especially around the eyes, muzzle, ears and feet. In severe cases the irritation is generalised. In cases where the allergens are seasonal the clinical signs of irritation are similarly seasonal, but many dogs with house dust mite allergy have perennial disease.
Some of the allergens associated with canine AD include pollens of trees, grasses and weeds, as well as molds and House dust mite. Ear and skin infections with the b
acteria Staphylococcus pseudintermedius and the yeast Malassezia pachydermatis are common secondary to canine AD. Flea allergy is commonly associated with AD. AD is a lifelong condition in most dogs.
Food allergy c
Diagnosis of AD is by elimination of other causes of irritation including fleas, scabies a
nd other parasites such as Cheyletiella and lice. Food allergy can be identified through the use of elimination diet trials in which a novel or hydrolysed protein diet is used for a minimum of 6 weeks and allergies to aeroallergens can be identified using intradermal allergy testing and/or blood testing (allergen-specific IgE ELISA).
Pemphigus foliaceus is the most common autoimmune disease of the dog. Blisters in the epidermis rapidly break to form crusts and erosions most often affecting the face and ears initially, but in some cases spreading to include the whole body. The pawpads can be affected causing marked hyperkeratosis (thickening of the pads with scale). Other autoimmune diseases include bullous pemphigoid and epidermolysis bullosa acquisita.
Treatment of autoimmune skin conditions requires treatment to markedly reduce the abnormal immune response; steroids, azathoprine and other drugs are used as immunosuppressive agents.