Horses, like people and other animals, can develop allergies to various substances called allergens that, when repeatedly inhaled or absorbed through the skin, respiratory tract, or gastrointestinal tract, can stimulate the immune system’s overreaction (allergic reaction). An allergic reaction mostly affects the skin or respiratory system and is typically triggered by insect bites, mold, dust, pollen, bedding, topical products, or food.
An allergic reaction of the skin, called atopic dermatitis, causes hives, bumps, crusting and hair loss on different parts of a horse’s body, both seasonally or non-seasonally. Additional skin symptoms can include swelling around the eyes and muzzle. Some breeds of horses are atopy-predisposed, including: Thoroughbreds, Quarter horses, Warmbloods, Arabians and Morgans. Other breeds of horses can develop allergies after an insect bite, these breeds include Welsh, Shetland, and Connemara ponies, as well as Arabian, German Shire, Friesian, and Icelandic horses. Respiratory allergic reactions that are widespread in horses can produce cough, labored breathing, nasal discharge, runny eyes, headshaking, and exercise intolerance that can even lead to chronic obstructive pulmonary disease or Equine Asthma Syndrome. Another type of allergic reaction in horses is a contact allergy which can be triggered by almost anything that contacts a horse’s body and produces signs typical to atopic dermatitis. Food allergies are not very common in horses and their signs are extremely variable including gastrointestinal or dermatologic swelling, or both in some cases.
Thus, allergic reactions that can turn into a chronic illness are frustrating and a potentially devastating part of a horse's life. All types of allergies tend to get worse over time with repeated exposure. Due to the overlapping signs of different types of allergies in horses, the most basic solution is to identify the source of the reaction. Allergy testing helps to identify the specific allergens that are problematic for each horse and is a cornerstone in the control of this disease. Early detection of offensive allergens minimizes the effect of disease on your horse’s health through a timely developed treatment plan and allergy vaccine formulation, if appropriate.
Skin and serological allergy tests are generally used for horse allergy detection. To perform the skin test, the horse is taken to a veterinary clinic where it is sedated and shaved, usually on the neck, before the allergen’s administration. If a horse is on medication, the results of a skin test could be obscured. Thus, serological tests are more practical in the field, because this test is more convenient for both the horse and its owner. For this method, a horse does not need to be sedated or shaved and there are no conflicts with existing medications. The vaccine, formulated based on the test results, is especially useful for show horses since the main medications used to control allergic reactions are prohibited or restricted by the U.S. Equestrian Federation and other show organizations. Using its new technologies, Pet Preferred Diagnostics is working on developing the equine allergy test that will be available for use soon. Please follow us on Facebook and LinkedIn for updates.