Improving Allergy Testing for Itchy HorsesBy Kentucky Equine Research Staff · August 30, 2017
Many of us have suffered from itchiness caused by chicken pox, poison ivy, or mosquito bites, but few of us have experienced the agony associated with unrelenting allergies or atopic dermatitis (AD). Horses with AD can itch so severely they lose hair from intense scratching, developing crusts, skin loss, redness, and hives on any part of the body including the face, ears, belly, and legs. In fact, a horse’s ability to work and general behavior can also change due to profound discomfort.
“No cure currently exists for AD, and treatment options are relatively limited, sometimes ineffective, and can be associated with adverse events,” explained Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research (KER).
In order to develop better treatment regimens, such as allergen specific immunotherapy, ASIT or “allergy shots,” researchers first need to accurately diagnose allergies and AD in horses. The current diagnostic tool of choice is intradermal testing (IDT). This involves injecting small volumes of allergens, such as molds, insects, grasses, or different grains, under the horse’s skin and noting whether the horse develops a reaction to the allergen, typically a swelling.
According to a recent study*, problems with the IDT include:
- If the concentration of allergen in the IDT injection is too high, even nonallergic horses may develop a reaction (i.e., a false-positive result);
- If the concentration of allergen in the IDT injection is too low, then false-negative results will occur; and
- Geographical location of an individual horse should be considered. Performing an IDT in a horse residing in the southern U.S. with grass or insect allergens obtained from the northern regions of the U.S. will be ineffective because horses in the southern U.S. would most likely not have been exposed to those allergens. In other words, individualized IDTs must be created for each region. The same holds true for horses elsewhere in the world, including Australia.
“These products contain full-fat soybean meal with B vitamins, biotin, iodine, chelated zinc, and methionine, all of which play a role in maintaining healthy skin, hair, and hooves,” explained Crandell.
*Lane, M.J., C.M. Pucheu-Haston, M.T. Kearney, et al. Determination of irritant threshold concentrations of multiple tree, grass, weed and mould allergens for intradermal testing of horses residing in the southern USA. Veterinary Dermatology. In press.