Everything You Need to Know About Allergies In Horses

As the warm weather is fast approaching, there are many things to look forward to around the farm. Whether it’s finally getting back into the outdoor area or giving your horse his first good scrub of the year. There is always a sense of freshness that comes with spring. Along with that freshness, come fields of lush grassy turnout and a few weeks of show-stopping pollen. Seasonal allergies are not the only culprit for your horses’ discomfort, though they tend to be the most common. It is important to understand what your horse is sensitive to and why the body responds in that manner. Here we will discuss the horses’ bodily responses to allergies, common signs your horse may be allergic to something, and what you can do to help alleviate these symptoms for your horse.

The Horses’ Immune System

With exposure to a substance that your horse is allergic to, the horses’ immune system kicks into high gear. The immune system targets what it perceives as a threat. In the case of a virus or infection, this would be an appropriate response. However, since there is no real invasion on the body, the reaction actually damages healthy body tissue. This reaction, paired with the now hypersensitivity to the allergen increases the chances and strength of the immune reaction the next time a horse interacts with the allergen.

When the body detects an allergen or any potentially harmful substance, the immune system releases an antibody. The antibody, immunoglobulin, sparks an inflammatory response in the body to attack the substance. This antibody is responsible for protecting the body. Another chemical reaction noticed in allergies is the release of histamine. Histamine also produces an inflammatory response but is most linked to the outward signs and symptoms of an allergen attack.

Seasonal Allergies

Symptoms of Allergies in Horses


Respiratory issues are an extremely common reaction to an allergy attack. The boost in inflammatory response from the body causes the nasal passages to narrow. This causes a decrease in the amount of oxygen permitted during a breath. It is especially important to address any respiratory issues you notice with your horse as it can interfere with their daily lives, performance or could be a more chronic condition like Heaves.


Hives are the most common visual symptoms of an allergy. Generally, hives are soft swollen spots across the body. These swellings can be small or large in size and range from one large hive to clusters across the body. Hives can develop from ingesting an allergen, direct skin contact with an allergen, or a reaction from an insect bite.


Less common than hives, some horses can develop swelling around the eyes, ears, muzzle, or reproductive areas due to an allergen response. More commonly, these reactions are due to skin contact or insect bite versus ingesting an allergen, though ingesting an allergen can also provide these results.


Due to the amount of hair on the body of the hose, a rash can be difficult to see. However, rashes are most often detected on “pink-skinned” horses. Itching is also another common response from interaction with an allergen. Sweet itch is the most common reaction seen due to the bites of Culicoides. Culicoides are small “gnat” like bugs that cluster on the underside of the belly and sometimes the neck. The infected area crusts over and becomes extremely itchy.


Anaphylaxis is the most extreme allergic response the body provides. Generally occurs in situations where an allergen has been exposed to your horse repeatedly. In this situation is it imperative to contact your vet immediately. When anaphylaxis occurs the horses’ blood pressure plummets and he struggles to breathe, the only way to reverse this reaction is for a vet to administer epinephrine immediately to raise the blood pressure along with dexamethasone to reduce the internal swelling and open airways. If not reversed immediately, the horse can go into shock and die.


Treating Allergies in Horses

While mild reactions can generally clear on their own, some cases will require veterinary intervention. There are many topical treatments available to help soothe the skin. Many times seasonal allergies will dissipate when pollen in the air subsides. Often other symptoms from an allergic reaction require treatment by administering a dose of dexamethasone to help alleviate the inflammation in the body. It is important to note that you should only treat with dexamethasone under veterinary approval as overuse of steroids can heighten your horse’s chance of laminitis and founder.

In more severe and chronic cases, your veterinary dermatologist can perform an allergy test. These tests consist of shaving an area of the skin and injecting small amounts of different allergens under the skin. Completed under sedation, horses are under surveillance for reactions from 15 minutes to 24 hours. The reactions undergo evaluation and a panel provides education to owners on their horses’ known allergies. Another form of testing is a blood test, though less accurate, they are easier to acquire and can be extremely helpful. After completing the testing, an owner can have a greater idea as to what substances should be kept away from their horse. In cases where there are multiple allergies or allergens that are somewhat unavoidable, allergy shots are generally administered per your veterinarian’s recommendation.

Excel Supplements and Your Horses Allergies

One of the best things you can do to help prevent allergic reactions within your horse is to keep him on a supplement high in omega-3 fatty acids. Supplements such as ExcelEQ and ExcelEQ ProElite provide a high dose of omega-3, aiding in promoting natural anti-inflammatory responses throughout the body. Providing your horse with a natural anti-inflammatory boosting supplement all year will significantly aid in keeping the body’s response level down when certain allergens arrive.


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