Dear Dr. Eisenberg,

Each spring my dog gets a severe rash on one of his front paws. He licks it and irritates it to the point that he has difficulty walking.

Itching for an answer

Dear Itching for an answer,

Dermatology, the study of skin, is one of the most complex areas of veterinary medicine. Many factors such as hereditary, hormonal, nutritional, behavioral, parasitic, infectious, and immune mediated can be involved in skin problems. Because of this complexity, skin disorders are often the most challenging cases for the veterinarian to help. The process involves the pet owner and the veterinarian working together. A thorough history of the problem, including past medications tried and the results from their use, needs to be provided.

With the history you describe, allergies may definitely be playing a role in your dog's condition. Assuming that the physical examination of your dog, including lab work, skin scrapings, biopsies, etc., are all consistent with this conclusion. Your dog may have a disorder called atopy, or Allergic Inhalant Dermatitis. This I a condition in which the pet becomes sensitized to environmental antigens due to genetic factors. Certain breeds that are known to have atopic tendencies include the Chinese Sharpei, Cairn Terrier, West Highland White Terrier, Scottish Terrier, Lhaso Apso, Shitzu, Dalmation, Pug, Boston Terrier, Golden Retriever, English Setter, Labrador Retriever, Schnauzer, and Wire-Haired Fox Terrier.

Dogs with atopy usually display pruritis (itching) and often have areas of scales, crusts, and small papules (bumps) on the skin. With pet atopy, the base membrane of the skin is attacked by the immune defense system and this leads to the skin problems displayed.

The treatment for atopy is difficult because often the underylying problem can never be resolved, only managed. One treatment may consist of allergy testing to determine the offending environmental antigens. Once these are isolated, either through intradermal skin testing or blood antibody testing, an allergy vaccine may be produced and given at specific intervals to help reduce the severity of the allergy.

Other forms of therapy involve the use of medicated baths to reduce the skin infections and itching caused by bacteria, yeast, and sebhorrhea often produced secondary to the atopy. These are usually used in conjunction with oral antihistamines, antibiotics, and topical creams.

Your pet is fortunate in that he suffers only seasonally. For pets that have seasonal problems, the treatment usually consists of trying to reduce exposure to the offending antigens, while giving medications to control the itching. For the year-round sufferers, hypoallergenic diets are often used to try and eliminate foods from being the source of the atopy. Often year-round sufferers are allergic to the bacteria, Staphylococcus that is normally found on their skin. This can often lead to the recurrent bouts of pimples or sores on the skin and must be treated with oral antibiotics.

As one can see, skin problems are very complex disorders that can be quite frustrating for the pet, the owner and the veterinarian. By realizing that the problem will not be remedied with a "quick fix", the level of frustration can be reduced.

Hope this helps you out!

Dr. Ken

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