Equine Skin Allergies

of itching that occur after topical treatments of shampoos dips etc. would be consistent with a contact allergy.
Intradermal tests IDT and serum blood allergy tests are often used to identify allergens responsible for hypersensitivity reactions. Similar to allergy tests in humans IDT involves injecting extracts from pollens molds and other environmental substances into the skin often in a grid pattern and measuring injection site responses anywhere from 30 minutes to a few hours later. Serum allergy tests are not always in agreement with IDT. Studies have reported variable repeatability for either method across time and individual animals which could be due to a variety of factors. Horses with atopic dermatitis and recurrent hives generally have a higher incidence of positive reactions than healthy horses.
Allergens identified as causing hypersensitivity reactions and interpreted in light of the horses known disease history clinical signs and elimination of other causes may then be used for hyposensitization therapy. Also known as allergen specific immunotherapy ASIT or allergy shots hyposensitization therapy involves administering small doses of an allergen on a gradually increasing basis to stimulate an immunological response. A study that evaluated treatment of cases of atopic dermatitis at the UC Davis veterinary hospital over 17 years noted an approximate 70 percent success rate in hyposensitization in horses a comparable study at the University of Pennsylvania reported similar results. Interestingly whether the hyposensitization is based on IDT or serum tests the success rate is approximately the same. There is now the option of using oral hyposensitization instead of injections.
The ultimate success of this type of therapy depends on adherence to instructions set forth by the veterinarian. This includes anticipating that injections will need to be administered usually by the owner or the horses caretaker for at least a year even if decreased clinical signs are observed
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