Pollen, bugs, mold…they’re everywhere. A little nutrition knowledge can go a long way to lessening your horse’s allergies.

This time of year is especially challenging for horse owners. Heat and humidity are certainly issues, but you also have an environment brimming with insects, pollen and mold. Your horse suffers from allergies, and so do you. Perhaps you’ve found that antihistamines offer some relief – but they can lose their effectiveness over time. Or you may have succumbed to corticosteroids – these “big guns” work quickly but cannot be used for the entire season. And steroids such as dexamethazone can induce laminitis in the insulin resistant or Cushing’s horse.

A Taxed Immune System

Anything that produces an allergic response stimulates your horse’s immune system to combat the problem. Histamines are released, along with inflammatory prostaglandins, leading to respiratory and skin reactions. If your horse has a healthy immune system, he may not be affected by environmental allergens such as grass pollen or insect stings. But even the best immune system can become exhausted from the constant bombardment of allergy-producing substances.

This is where nutrition comes into the picture. The goal is to bring your horse’s overactive immune function back into balance. Key nutrients can go a long way toward protecting him against allergies. The following nutritional approaches are worth considering during allergy season:

• Quality protein:
Antibodies that counteract allergens are made of protein. In order for your horse to produce enough antibodies, he needs to have an adequate variety of amino acids (the building blocks of protein). Grass hay offers some amino acids, but is not complete. A legume, such as alfalfa (clover and soy are also legumes), will boost the overall protein quality because it contains different amino acids.

• Omega 3s:
These fatty acids actually stabilize the immune system. If your horse is grazing on healthy pasture for at least eight hours a day, he is getting enough Omega 3s. If not, Omega 3s can easily be provided by adding flaxseed meal or oil to the diet. The best way to feed flaxseeds is to grind them. Do not feed whole flaxseeds since most will not be digested. And do not soak them, since water promotes oxidation (destruction) of these fatty acids. Instead, feed a commercial flaxseed meal that is stabilized against rancidity.

√ Flaxseed meal – 1/2 cup per 400 lbs of body weight
√ Flaxseed oil – 2 tablespoons per 400 lbs of body weight
√ Chia seeds are also a good source of Omega 3s use 1/3 cup per 400 lbs of body weight
√ Fish oils can be added in extreme cases – Reduce flax or Chia seeds by half and add 2,000 mg fish oils per 400 lbs of body weight

• Minerals:
A comprehensive vitamin/mineral supplement will generally cover all your bases regarding mineral intake, but disproportionate amounts can occur when the hay and/or pasture is out of balance. Copper and zinc in particular are important players in immune function; they should ideally have a 4:1 ratio of zinc to copper.

Iodine and selenium need to be present in the proper amounts. Too much iodine, without enough selenium, can damage the thyroid gland, while too much selenium can be toxic. A safe iodine level is between 1 and 6 mg per day. Selenium levels can safely range from 1 to 3 mg per day for maintenance (up to 5 mg per day for intense activity).

• Antioxidants:
Many antioxidant supplements contain beneficial ingredients like quercetin, lipoic acid, grapeseed extract, and even coenzyme Q10. These are all worthwhile. But several vitamins also have the ability to neutralize damaging free radicals (the role of an antioxidant).

A healthy pasture is the best source of vitamins for your horse. Once cut, dried and stored to make hay, it loses many key vitamins, including C, D and E as well as beta carotene (your horse uses this to make vitamin A). Omega 3 fatty acids are also virtually non-existent in hay. Vitamin C is not only an antioxidant but also has antihistamine properties.

√ Vitamin C – 20 mg per lb of body weight
√ Vitamin E – 8 IU per lb of body weight
√ Vitamin A – 50 IU per lb of body weight

• B vitamins:
The microbial population in your horse’s hindgut is capable of producing B vitamins. But when the immune system is compromised, additional B vitamins offer protection for many bodily systems. Though not scientific, there is much anecdotal evidence to suggest that vitamin B1 (thiamin) at 1,000 mg a day repels insects. A B- complex preparation (without added iron) is an excellent choice.

• Herbs:
Spirulina has been shown to be especially effective for upper respiratory allergies, as well as itching and skin allergies. Give your horse 2 grams per 100 lbs of body weight, twice daily – that’s equivalent to two level tablespoons, twice daily, for the 1,000-lb horse. Another herb, Jiaogulan, at 2,000 mg twice daily, is also helpful. Stay away from garlic, as it can cause Heinz Body Anemia. Commercial garlic preparations often heat the garlic, which makes it safe but less effective at repelling bugs (though it has just as strong an odor!).

• Apple cider vinegar:
This is another ingredient that many horse owners have been using over the years to reduce insect bites. You can add 4 ounces to a 5-gallon water tub or to your horse’s meal.

Hydration is Key

Water is needed to thin mucous secretions and allow irritants to be expelled from the horse’s lungs. A full-sized horse will drink between eight and 12 gallons of water each day. Always have fresh, clean water close by (without algae growth, dead insects or bird droppings). Keep your horse’s thirst mechanism working properly by adding salt to the diet. A minimum of two tablespoons of plain white table salt is required every day. Many horses do not adequately lick a salt block, and therefore should either have granulated salt offered free choice, or one tablespoon added to each meal. Salt provides sodium – an electrolyte in which hay and pasture are deficient. It also provides chloride, to further promote fluid balance.

Beware of Moldy Hay

If you see an area of hay that’s clumped together, is black or even white with lots of dust, that’s mold, and spores are likely to be dispersed throughout the entire bale. The ideal situation would be to discard the whole thing. This may not be the budget-friendly thing to do, but it is the only way to eliminate risk. You could discard the moldy area from that bale and offer the rest of it along with hay from another bale to see which one your horse will eat. If provided with a choice, you may find he won’t eat from the hay bale that had mold.

Pay Attention to Hindgut Microbial Population

The microbes that live in your horse’s hindgut (cecum and large colon) are not only responsible for digesting fiber and producing B vitamins, but they also protect the immune system. Promote good numbers by providing yeast (Saccharomyces cerevisiae) as well as oligosaccharides. A good pro/prebiotic formulation will contain these two ingredients.

Genetic Factors

Allergies may be linked to the genetic predisposition of your horse. But that doesn’t mean the gene has to be “activated” to reveal symptoms. A horse with a healthy immune system may go unscathed by environmental irritants, while another horse of similar genetics may be miserable because his immune system just cannot handle the onslaught of allergens.

Finally, Reduce Stress

Nutrients are “tools” that help your horse battle the pollens and insects to which he’s exposed. But don’t forget his stress level – stress suppresses the body’s ability to fight infection, making him more susceptible to developing allergies. Hot humid weather is stressful. Take means to protect him from heat-related illness. And most importantly, respect his need to graze on forage continually throughout the day and night by offering hay and/or pasture, free choice.

Keep your horse happy. Fresh air, exercise, good food and the company of other horses all do wonders in keeping the immune function at its peak performance. A happy horse is a healthy horse!

Juliet M. Getty, PhD is a consultant, speaker, and writer in equine nutrition. A retired university professor and winner of several teach ing awards, Dr. Getty presents seminars to horse organizations and works w th individual owners to create customized nutrition plans designed to prevent illness and optimize their horses’ overall health and performance. Based in beautiful rural Bayfield, Colorado, Dr. Getty runs a consulting company, Getty Equine Nutrition, LLC (, through which she helps horse owners locally, nationally and internationally. The well being of the horse remains Dr. Getty’s driving motivation, and she believes every horse owner should have access to scientific information in order to give every horse a lifetime of vibrant health.


Dr. Juliet M. Getty earned her Master of Science degree in Animal Nutrition at the University of Florida. She completed her doctoral coursework in Animal Nutrition at the University of Georgia, and continued her studies at the University of North Texas, where she earned her PhD. Winner of several teaching awards, Dr. Getty has taught comparative nutrition studies at the University of North Texas for 20 years. At the same time, she has been working in the field, consulting privately with horse owners to customize feeding plans that address a variety of health conditions. Recently retired from academia, she now resides in Denton, Texas, where she devotes herself full-time to equine nutrition. Through her consulting company, Getty Equine Nutrition, she provides consultations locally, nationally and internationally.