Food Allergy Testing In Horses: Latest on IgE

Despite being available for years, allergy testing in horses continues to provide “inconsistent results,” according to a group of European equine nutritionists in a recent study*.

“Food allergies are an increasingly common finding in many species, including humans, dogs, cats, and potentially horses,” explained Kathleen Crandell, Ph.D., an equine nutritionist for Kentucky Equine Research (KER), located in Versailles, Kentucky.

Although poorly described in horses, possible clinical signs suggestive of food allergies include hives (uticaria), itchiness (pruritus), changes in fecal consistency, and colic.

One method of diagnosing dietary allergies is through a blood test. In other species, the immunoglobulin E (IgE)-based blood test has consistently proved unreliable at best. Because equine IgE blood tests have not been assessed for reliability in horses, Dupont and colleagues collected samples from 17 healthy Shetland ponies and submitted them to a single laboratory for analysis. They found:

• Six of the 17 tested ponies were positive in a general test for “yes” or “no” to an allergy;
• Blood from the six positive horses was subsequently tested for specific food allergens. They tested positive for one or more of the following: corn, soy, sugar beet, oats, alfalfa, and rye;
• Based on those results, the ponies with positive results underwent “provocation trials,” meaning they were fed items they were allegedly allergic to; and
• None of the ponies undergoing the provocation trials developed signs of dietary allergies (e.g., altered heart rate, temperature, urticarial, itchiness, etc.).

“This study concluded that the specific commercial blood test used in this study was not a reliable indicator of the presence of food allergies in horses,” summarized Crandell. “That said, this study only used a single laboratory and did not include any horses with confirmed food allergies as a comparison.”

The researchers added, “Misleading results from this commercially available test can lead to unnecessary or inappropriate changes in food management when eliminating the presumed food allergens from the daily ration.”

Owners that believe their horses have a food allergy are advised to consult a veterinarian and equine nutritionist to discuss appropriate, feasible, and healthy dietary changes. Remember that omega-3 fatty acids have natural anti-inflammatory properties and benefit patients with allergies and asthma**. EO•3, a product developed by KER, is a palatable, marine-derived supplement containing both EPA and DHA that is top-dressed onto the feed.

Omega-3 fatty acids also benefit other body systems, including respiratory and musculoskeletal function.

*Dupont, S., A. De Spiegeleer, D.J.S. Liu, et al. A commercially available immunoglobulin E-based test for food allergy gives inconsistent results in healthy ponies. Equine Veterinary Journal. In press.

**Willemsen, L.E. 2016. Dietary n-3 long chain polyunsaturated fatty acids in allergy prevention and asthma treatment. European Journal of Pharmacology. 785:174-186.