Allergy Testing
Atopy is a genetic, dermatologic, or respiratory condition that develops when horses develop sensitizing antibodies to environmental allergens such as bedding, feed, tack, plants, and insects in the immediate area. A sensitizing antibody is produced which stimulates the release of histamine and other inflammatory mediators.
The clinical signs of atopy are wheezing, itching, hives, hair loss, and thickened and inflamed skin. Skin testing for offending allergens has been available for many years. Horses respond to skin testing and hyposensitization better than man and the other domestic species. To perform skin tests, a small amount of a known allergen is injected into the skin and evaluated 30 minutes later. Control sites of sterile water and dilute histamine provide a negative and positive response for comparison. A positive test is characterized by swelling of the skin at the injection site within
twenty minutes.
Presently, we use 47 different antigens for testing. Once the offending antigens are identified, a suspension is compounded containing small doses of the antigens that caused swelling. A measured dose is injected into the patient weekly. After several months of desensitization, many horses improve dramatically. If your horse has seasonal skin or respiratory allergies, desensitizing therapy may be the best approach.