Like many humans, horses can also develop seasonal allergies, and the symptoms can be as varied as they are with humans. Some of the common allergens for horses are the same as they are with humans, but an individual horse can be allergic to highly specific substances. With hundreds of plants and trees pollinating at some times of the year, it can be difficult to pinpoint the exact culprit. In a large herd of Arabians, for example, one mare alone may break out in silver-dollar-sized hives when the jack pine trees pollinate each spring. For another stallion in the same herd, it might be a reaction to a particular brand of grooming cleanser.
Causes of Allergies in Horses
Allergic reactions in horses may also be characterized as hives (urticaria), dermatitis, or hypersensitivity. If anything, horses may be even more susceptible to allergic reactions than are humans. Many substances can cause allergic reactions in horses, and there are some people who strongly feel that horses are becoming more sensitive due to pollution in our air, food, and water. Some common, well-known allergens for horses include:
- Feeds and fodders, including weeds that horses should not (but do) eat
- Pollen from weeds, gardens, and trees
- Grooming sprays
- Fly sprays
- Synthetic chemicals or finishes on equipment
- Dust and molds
- Medications or supplements
- Crop sprays and other chemical treatments applied to feed crops or drifting from neighboring fields
- Stall bedding materials
In short, anything that your horse can ingest, inhale, or come into contact with can potentially cause an allergy. While most horses can cope with most allergens, some horses (like some people) develop deep, even life-threatening sensitivities, for no obvious reason.
Common Symptoms of Allergies in Horses
Many allergic reactions in horses start out with hives—the hair stands up slightly, and you can feel a raised bump on the horse's skin. Hives can be tiny or quite large. Eventually, the hair may fall off of the hives, leaving behind tender patches of skin. There may also be flakes of dander and itching or sensitivity. Hives often disappear as mysteriously as they've appeared, while other allergic reactions take longer to clear up. Horses may rub their tails on fence posts or scrub their manes out by scratching their necks on feeders, branches, or trees.
If pollen or another inhaled irritant is causing the problem, your horse may also cough, have a slightly runny nose and eyes (some clear discharge is perfectly normal), or have slightly raspy breathing. Severe allergic reactions might include edema—noticeable swelling caused by the collection of watery fluid in tissues. Contact dermatitis—a visibly irritated patch of skin—can appear as a sensitive area where a piece of equipment has been in contact with the horse, or where a substance such as a grooming lotion or bug spray has soaked through the hair.
Allergic reactions tend to come and go quickly, and in some cases, your horse may be over the symptoms before you've figured out what caused them. You may find the horse reacts at the same time each year, or perhaps never again. If the allergies don't clear up quickly and are causing you or your horse a lot of distress, veterinary testing may help determine what is triggering the allergy.
Corticosteroids or antihistamines can be helpful to quell the reaction. Some owners feel they've had success with supplements that boost immunity, such as omega-3 fatty acids, blue-green algae, and traditional Chinese medicine (TCM). Itching and irritation can be treated with soothing topical washes, ointments, or lotions.
The only sure way of preventing an allergic reaction is to separate the horse from the allergen. This may be easier said than done, as it may take extensive (and expensive) testing to find out what exactly is causing the allergic reaction. Once the allergen source is determined, you must either remove the source or move the horse to another location where the allergen is no longer present. Sometimes neither is possible, such as when a particular plant species is very widespread over an entire region.
For horses with severe, unavoidable allergies, your veterinarian should be able to provide you with medications to combat the symptoms. If the horse is very distressed, however, relocation may be the only solution.