Feeding an itchy horse starts with boosting omega-3 fatty acids and reducing dietary triggers that fuel inflammation. The right combination of fats, vitamins, and minerals can meaningfully reduce allergic skin reactions, but you also need to watch what you cut from the diet, not just what you add.
Flaxseed: The Best-Studied Option
Ground flaxseed is the most research-backed feed for itchy horses. In a study published in the Canadian Journal of Veterinary Research, horses with allergic reactions to biting midges (Culicoides) showed significantly smaller skin lesions after six weeks of flaxseed supplementation compared to horses on a placebo. The difference became statistically significant by day 42.
The effective dose in that study was 1 pound of milled flaxseed per 1,000 pounds of body weight per day. For a typical 1,100-pound horse, that works out to roughly 1.1 pounds (about 500 grams) of ground flaxseed mixed into the daily feed. Flaxseed must be ground or milled for horses to absorb the fats inside. Whole seeds pass through largely undigested. You can grind it fresh in a coffee grinder or buy it pre-milled, but pre-milled flax goes rancid faster and should be stored in a cool, dark place.
Flaxseed works because roughly 55% of its fat content is alpha-linolenic acid, a plant-based omega-3 fatty acid. Omega-3s dampen the inflammatory pathways that drive itching, while omega-6 fatty acids promote them. Fresh pasture naturally has an omega-6 to omega-3 ratio of about 0.3 to 1, which is ideal. Hay shifts to about 0.6 to 1. Grain-heavy diets push the ratio much higher in the wrong direction. Adding flaxseed helps correct that imbalance.
Chia Seeds as an Alternative
Chia seeds are another strong source of omega-3s, with about 59% of their polyunsaturated fat as alpha-linolenic acid, slightly higher than flaxseed. They also contain more antioxidants than flax due to their polyphenolic compounds. Chia seeds form a mucilage gel when they contact water, which can help soothe gut irritation and reduce bowel inflammation, a useful bonus since gut health and skin health are closely linked.
One limitation worth knowing: the plant-based omega-3 in both chia and flax (ALA) has to be converted in the body to the more active forms, EPA and DHA, and horses convert only about 10% of ALA to EPA and less than 0.1% to DHA. This means plant-based omega-3 sources help, but they won’t match the potency of fish oil or marine-derived EPA and DHA supplements designed for horses. If flaxseed alone isn’t resolving the itch, a supplement containing direct EPA and DHA may be worth adding.
Cut the Sugar and Starch
What you remove from the diet matters as much as what you add. High-starch, high-sugar feeds can worsen systemic inflammation. Sweet feeds, molasses-coated grains, and cheap pellets with fillers tend to be loaded with non-structural carbohydrates (NSC). For horses prone to inflammatory skin conditions, keeping the total diet below 10% NSC is a widely cited guideline, originally aimed at horses with insulin problems but increasingly applied to any horse dealing with chronic inflammation.
In practical terms, this means replacing sweet feeds with low-NSC alternatives like beet pulp (without molasses), soaked hay, or forage-based pelleted feeds. If your horse is on pasture, be aware that spring and fall grass can spike in sugar content, especially on sunny mornings after cold nights. Soaking hay for 30 to 60 minutes in cold water leaches out a significant portion of soluble sugars.
Vitamin E for Skin Repair
Vitamin E is a powerful antioxidant that protects skin cells from oxidative damage, and many horses don’t get enough of it, particularly those on hay-only diets. Fresh pasture is the primary natural source, and vitamin E degrades rapidly once grass is cut and dried. A horse eating only hay could easily be deficient.
The general recommendation for adult horses is 1,000 to 2,000 IU per day, though horses under oxidative stress from skin conditions or exercise may benefit from the higher end of that range. The National Research Council’s baseline requirement is 1 IU per kilogram of body weight for maintenance, which works out to about 500 IU for a 500-kilogram horse. That’s considered the minimum, not the therapeutic target for a horse with active skin issues. Natural, water-soluble vitamin E absorbs better than synthetic versions and can be top-dressed directly onto feed.
MSM for Skin and Coat Support
MSM (methylsulfonylmethane) is a sulfur-donating compound that supports the production of keratin and collagen, the structural proteins in skin, hair, and hooves. Sulfur is essential for building and repairing these tissues, and MSM provides it in a highly bioavailable form.
Research-informed dosing for horses is typically 10 to 20 grams per day for a 500-kilogram horse. At 20 grams per day, studies have demonstrated measurable anti-inflammatory effects. Some products recommend 2 grams per 100 kilograms of body weight, which aligns with that same range. MSM is considered very safe and can be combined with other supplements. It won’t stop itching on its own, but it supports the skin’s ability to heal and rebuild between flare-ups.
Spirulina and Antioxidant Support
Spirulina, a blue-green algae, has gained popularity as an anti-allergy supplement for horses. It acts primarily as an antioxidant, scavenging reactive oxygen species that contribute to tissue inflammation. In a study on horses with lower airway inflammation, a supplement containing 12% spirulina alongside vitamins C and E reduced mucus buildup and coughing over a 21-day period, likely through its antioxidant activity rather than direct immune suppression.
While the research on spirulina for equine skin itching specifically is limited, its mechanism of reducing oxidative stress is relevant to any inflammatory condition. Typical supplementation runs around 15 to 30 grams per day for a full-sized horse, though products vary. It’s best used as part of a broader anti-inflammatory diet rather than a standalone fix.
Putting the Diet Together
A practical anti-itch feeding plan combines several of these elements. Start with a forage-based diet that’s low in sugar and starch. Add ground flaxseed or chia seeds daily for omega-3s. Supplement with 1,000 to 2,000 IU of natural vitamin E, particularly if your horse has limited pasture access. Consider 10 to 20 grams of MSM for skin repair support.
Give dietary changes at least six weeks before judging results. The flaxseed study didn’t show significant improvement until day 42, and that timeline is typical for nutritional interventions. Skin cells turn over slowly, and shifting the body’s inflammatory balance takes time. If you’re adding multiple supplements, introduce them one at a time over a few weeks so you can identify what’s actually helping.
Keep in mind that no feed change will fully resolve itching caused by external factors like insect bites, contact allergies, or fungal infections. Diet is one layer of management. But for horses with Culicoides hypersensitivity, sweet itch, or general inflammatory skin conditions, the right nutritional foundation can reduce the severity and frequency of flare-ups in a measurable way.