The percentage of horses that suffer from food allergies is unclear because these animals are often improperly diagnosed or their food reactions are noted and corrected before being reported to a veterinarian. Pinpointing the cause of a food allergy, then avoiding the offending substance, can be a difficult process, but it is a necessary one, according to Dawn Logas, DVM, Dipl. ACVD, of the Veterinary Dermatology Center in Maitland, Fla. She addressed veterinarians and feed company representatives at the Kentucky Equine Research meeting held Oct. 25-26 in Lexington, Ky.

Saying that your horse has a "food allergy" implies that he’s had an immunologic reaction to something he ate. But not all food "allergies" are truly allergic in nature, according to Logas�a horse could be having an immune or non-immune response. "A better term for the condition would be �adverse reactions to food,’ " although the former is still generally used, she said.

Most research into food allergies has focused on human food hypersensitivities. All of the different clinical signs of food hypersensitivities in humans have been noted in horses, but detailed information about each type of reaction (each type is evidenced by a different type of appearance: lesions vs. discoloration, for example) is lacking in horses.

The Science of Hypersensitivity
For any hypersensitive reaction to occur, sensitization must first happen, during which an antigen is repeatedly presented to T lymphocytes (white blood cells that help control cell-mediated immunity and control the development of other white blood cells that are involved in the production of antibodies to combat infection) and an abnormal hypersensitivity response occurs instead of tolerance. To cause a food allergy, an allergen must pass the intestinal mucosal barrier in order to be exposed to the immune system of the horse, and typically the intestinal tract prevents the absorption of these potentially allergenic substances