Q. My 17-year-old Arabian gelding horse began breaking out in hives last summer. Maybe it was something in the field, maybe it was bugs; I’m not totally sure. Is there anything I can do nutritionally to help him be prepared for the onslaught of whatever causes his allergies this year?

A. It is no fun managing a horse that struggles with allergies, and allergies aren’t fun for them either. An allergic reaction is a hypersensitivity reaction caused by a pathological immune response to a per se harmless substance. For example, getting bitten by a horsefly should not result in a significant immunological response. However, if your horse has an allergy, his immune system sees this bug bite as the ultimate insult, initiating an overreaction.

The immune system generates something called immunoglobulin E (IgE) antibodies, which travel to cells that then release inflammatory mediators that cause the allergic reaction. These mediators might have immediate effect in as little as five to 15 minutes—think anaphylactic shock in people with severe nut allergy—or the reaction might take considerably longer. Clinical signs of allergic reactions are normally seen on the skin and in the airway (nose, throat, lungs).

Each allergen results in its own specific IgE, so your horse might only be allergic to bug bites and produce that IgE, or he might also be allergic to a specific tree pollen that generates that IgE, as well. Just like people, horses can be allergic to many things in their environment. Symptoms can be cumulative. So, it’s possible he is allergic to both grass and pollen in the field, and those alone doesn’t result in very severe or obvious symptoms. When you add bug bites, however, the combination results in an overt allergy response.

It is possible to get your horse tested to try to narrow down what he’s allergic to, and this can help you manage his environment so he comes in contact with fewer allergens. For example, if he is allergic to mosquitoes, pine shavings, and grass pollen, you could turn him out at times of day when mosquitoes are less prevalent. If he is in a stall at other times, you could use fans to help keep the bugs off him, as well as fly sheets when he is out. Changing your bedding to make sure you are not exposing him to pine shavings will help, as will managing your pastures so he is turned out on fewer flowering grasses. Sometimes just removing or reducing exposure to a couple of known allergens can make a big difference in the symptoms the horse develops.

Because the reaction to the IgE is inflammatory, supporting your horse with proper nutrition for a healthy inflammatory response can help. Omega-3 fatty acids are my first step. I recommend plant-based omega-3 sources such as flax for most of the horses I work with, if they do not have access to good-quality pasture. Omega-3 fatty acids are abundant in fresh grass but are not heat-tolerant and are lost during the hay curing process. This means horses on predominantly hay-based diets might be consuming low levels of this important fatty acid.

Flax comes whole, ground and stabilized, and as oil. My preference is for ground and stabilized, because the outer shell on whole flax is hard and might not get broken when chewed, which would make the contents potentially less available to the horse. Other plant-based oils with good omega-3 levels are camelina oil and ahi oil. Camelina and flax are very similar, although camelina is a more stable oil and, so, a good choice if you live in a hotter climate. Ahiflower oil is unique due to the type of omega-3 it contains. Most plant sources of omega-3 are in the form of linolenic acid that is then metabolically converted to the forms the horse ultimately needs, docosahexaenoic acid (DHA) and eicosatetraenoic acid (EPA). This conversion process has multiple steps, and it does not always function efficiently. Ahiflower oil is somewhat unique in that it also contains an omega-3 fatty acid called stearidonic acid (SDA). It, too, is converted to DHA and EPA, and its conversion is more efficient than the conversion of linolenic acid.

For horses with severe allergies, it can be worth bringing out the big guns and supplementing EPA and DHA directly. There are several fish-oil-based products for horses on the market. They are not always the most palatable and might need to be administered via oral syringe until the horse gets used to the smell and taste. Another source of DHA is algae, which is sold alone or in allergy supplements that might also provide other compounds thought to help mediate allergic response, such as quercetin.

Another area of support I like to provide horses with allergies is digestive health. The digestive tract is a major component of the immune system, so anytime the digestive tract is inflamed or not functioning optimally, there is a risk of elevated systemic inflammation. If inflammation already exists in the horse’s body and an allergic insult is added, you might see more severe inflammatory responses to an allergen.

Ingredients such as butyric acid (which helps mitigate leaky gut, ensuring the cells that line the digestive tract remain tightly adhered to each other) and Saccharomyces cerevisiae yeasts (brewer’s yeast) and their byproducts (which help stabilize the hindgut and bind and remove bad bacteria so they cannot attach to the intestinal wall) all help regulate inflammation.

By understanding your horse’s allergens, managing his environment, and selecting targeted dietary ingredients carefully, you can give your horse the best chance of being allergy-symptom-free this summer. The earlier you initiate these steps, the better chance your horse will have of getting out in front of the things that make him itch.