Richard Mansmann, VMD, PhD, director of the Equine Health Program at North Carolina State University, says observations by the horse owner (such as keeping a diary of what is done with the horse and when) are crucial in helping the veterinarian pinpoint the cause of an allergy problem.
Once the things that trigger an allergic reaction are determined, those can be avoided.
"In these odd cases, a complete history of the horse is a lot less expensive, and usually more effective, than going through a lot of diagnostic tests," says Mansmann
Hives are a common allergy problem in horses.These lumps might be triggered by reaction to a certain plant (ingested or contacted by the skin), fly bites, ingredient in a fly spray or shampoo, or reaction to the carrier in a vaccine.Some horses develop chronic hives, and it's difficult to pinpoint the cause.
"A skin biopsy can tell you it's an allergic reaction, but won't tell you the cause," says Mansmann
."Skin testing may help, but not if the horse already has bumps all over the body; it's hard to find a place to put the injections for the test," says Mansmann
For skin testing, usually the neck is shaved and various allergens are injected intradermally in a grid pattern.
says the best solution for a horse with chronic hives is treatment with a low dose of corticosteroid."I also use an antihistamine type of drug, hydroxyzine," he