While it may feel like winter will never end, rest assured that spring is right around the corner and for many horses this means seasonal allergies. Seasonal allergies can range from pollen in the air to biting insects but regardless of cause, they can make horses uncomfortable and cause owners a great deal of worry. Allergies to pollen typically present themselves as airway issues, coughing when working, breathing problems, and may be diagnosed as equine asthma. Reactions to biting insects result in skin sensitivity, itchiness, rubbing manes and tails and sometimes hives. The good news is that there are ways that you can support your allergy prone horse through targeted supplementation.

Why do Allergic Reactions Happen?

An allergic reaction is the result of how the horse’s body reacts to a foreign protein (allergen). It is an overreaction to an otherwise harmless substance. The first time this allergen is encountered, the body responds by creating an immunoglobulin called immunoglobulin E (IgE). These antibodies can bind to allergy cells called mast cells that are found in the skin, airway and digestive tract. When the IgE comes into contact with the allergen in the future, it binds it and takes it to the mast cell for removal. In response to being brought an allergen, the mast cells release histamine which is one of the mediators of allergic reactions. It is the primary cause of mucus secretion, sneezing, and hives. 

Histamines’ job is to help keep allergens out of the body. By stimulating inflammation, mucus, sneezing, coughing, constricting airways etc. less allergen will come into contact with tissue where it will cause a reaction. In the airway, histamine can cause the muscles in the lungs to contract making it harder to breathe. Swelling and mucus in the airway makes it less likely that an allergen will reach the lung lining and stimulate a response, but it also makes it harder for oxygen and carbon dioxide to transfer across lung tissue. This can result in the loss of breath most commonly associated with asthma. In the skin, histamine release can result in swelling and itchiness. 

Evidence that Omega-3 Fatty Acids Help!

There is a growing body of evidence that omega-3 fatty acids have a beneficial effect on chronic inflammatory diseases in people such as asthma, inflammatory bowel disease and rheumatoid arthritis. Research shows that the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosapentaenoic acid (DHA) are the precursors to compounds called resolvins and protectins which are specialized pro-resolving mediators (SPM) (1). Their job is to mediate inflammation. 

A lot of research has been done on human subjects that indicates a protective effect and possibly a causal relationship between decreased intake of fish oil in modern diets and an increasing number of individuals with asthma or other allergic diseases. In fact, studies suggest that SPM synthesis is impaired in those with severe asthma meaning that they are unable to resolve the inflammation in their lungs (2). An epidemiologic study of young adult Americans found that a high intake of omega-3 fatty acids, in particular DHA, prevented asthma onset. 

Fish Oil – Benefits for Horse and Human Alike

The benefit of omega-3 fatty acids on managing airway inflammation and other allergic responses is not limited to human research. Work by Nogradi et al., (3) looked at whether the addition of polyunsaturated fatty acids in the diet of horses could increase plasma levels and in turn improve clinical symptoms of inflammatory airway disease (IAD) and recurrent airway obstruction (RAO). Using horses diagnosed with these conditions they fed a complete pelleted low dust diet and fed either 30 or 60 grams of a supplement containing DHA or 30 grams of placebo. They found that feeding the DHA containing supplement for 2 months resulted in a peak in plasma DHA at 4 weeks and a 60 percent improvement in cough score, and a decrease in respiratory effort of 48 percent compared to an improved cough score of 33 percent and decreased respiratory effort of 27 percent in the control group. The researchers noted that the results with the DHA supplement were similar to those seen with a 3-week course of dexamethasone steroid without diet modification. 

Omega-3 fatty acids may also aid horses prone to biting insect sensitivity. In horses that were diagnosed with Culicoides spp. hypersensitivity and fed 200 ml of linseed oil or corn oil for 18 weeks, owners reported an improvement when supplemented with the linseed oil (4). Linseed oil is rich in the omega-3 alpha-linolenic acid (ALA) however it is not as potent as EPA and DHA. 

While there are a number of plant-based omega-3 options that provide ALA, EPA and DHA are only available from marine sources such as marine algae and cold water fish. ALA must be converted to DHA and EPA since these are the active forms of omega-3 in the horse’s body. While the horse is capable of this conversion process, it is not very efficient. Therefore, a far better approach to promoting a healthy inflammatory response is to supplement the EPA and DHA directly.  

A Source of Marine Derived DHA and EPA

Equine Omega Complete provides a source of marine derived DHA and EPA mixed with organic cold pressed soybean oil that the majority of horses find very palatable. These important fatty acids are also available in Equine Omega Vitamin E for horses needing more vitamin E support.

As shown by the research studies available, it can take several weeks to reach maximal plasma concentrations of DHA and therefore it is recommended when using DHA to support horses with seasonal allergies that supplementation start well ahead of when allergen exposure is expected. With only a few weeks until the weather turns that means you need to start supplementing your allergy prone horse now!

1. Serhan CN, and Levy BD.Resolvins in inflammation: emergence of the pro-resolving superfamily of mediators. J Clin Invest. 2018;128(7):2657-2669. https://doi.org/10.1172/JCI97943.
2. Miyata J, Arita M. Role of omega-3 fatty acids and their metabolites in asthma and allergic diseases. Allergol Int. 2015 Jan;64(1):27-34. doi: 10.1016/j.alit.2014.08.003. Epub 2014 Oct 27. PMID: 25572556.
3. Nogradi N, Couetil LL, Messick J, Stochelski MA, Burgess JR. Omega-3 fatty acid supplementation provides an additional benefit to a low-dust diet in the management of horses with chronic lower airway inflammatory disease. J Vet Intern Med. 2015 Jan;29(1):299-306. doi: 10.1111/jvim.12488. Epub 2014 Oct 10. PMID: 25307169; PMCID: PMC4858086.
4. Friberg, Logas. Treatment of Culicoides hypersensitive horses with high-dose n-3 fatty acids: a double-blinded crossover study. Vet Dermatol. 1999 Jun;10(2):117-122. doi: 10.1046/j.1365-3164.1999.00147.x. PMID: 34644932.