Several conditions in horses are related to allergies. Many horses are allergic to flying insects as well as other allergens, and they develop skin disease because of the itching. Late in the year is not a common time for skin allergies but it is a common time of year for allergies affecting the respiratory system. Heaves, also called recurrent airway obstruction, is a chronic condition characterized by difficulty breathing and it has been shown to be allergy related. This condition becomes more common in the winter as many people stall their horses more due to the cold weather, and some of these horses are allergic to allergens in the barn.
Allergy tests are available to determine the antigens to which the horse is sensitive. There are two types of allergy testing. The first is the skin prick test in which a small skin prick is made on the horse’s skin and various possible allergens are injected to determine if the horse has an allergic reaction. The second is a blood test that checks for various immunoglobulins. A study was recently performed in Portugal and published in the Journal of Equine Veterinary Science to determine the efficacy of the skin versus the blood test for allergies in horses. The results indicated that blood testing is not reliable for the diagnosis of the allergens that cause heaves in horses and the skin prick test performed better overall. So if you have a horse with heaves or allergic airway disease, it is probably better to contact a veterinary dermatologist to perform skin testing rather than blood testing to determine the allergens causing the condition.