It’s summertime and the bugs are out in full force. You notice that your horse’s reaction is more severe than you’ve remembered. Instead of the typical, minor bumps from fly bites, there are more of them, including large, painful welts. You’ve tried fly sprays, sheets, and traps, but the problem persists.
When an allergic reaction to bug bites goes into overdrive, it is known as Insect Bite Hypersensitivity (IBH), or "Sweet Itch." What are your options when your regular fly control isn't enough?
◆︎ Classic Signs
While standard fly bites can happen anywhere, true Insect Bite Hypersensitivity (IBH), caused by midges has a distinct pattern. Midges typically target the mane, the base of the tail, and the belly. If you notice your horse developing a "rat tail" from rubbing the hairs off the dock, a rubbed-raw crest, or crusty scabs exclusively along their belly, you are likely dealing with Sweet Itch rather than typical fly irritation.
◆︎ Identify the cause and improve the environment
To best help your horse, you must identify the primary cause. While regular stable flies and horse flies are a nuisance, true IBH is most commonly caused by Culicoides (biting midges or "no-see-ums"). Other culprits can include black flies, mosquitoes, fire ants, and bees.
➡ Barrier Protection: The use of fly sheets, fly masks, and fly boots is essential. While barriers won’t heal existing bumps and welts, they drastically reduce the number of new bites.
➡ Apply "Greasy" Barriers: Fly sheets are excellent, but a horse's belly and the insides of their ears are notoriously hard to protect. Apply a thick layer of ointment—such as petroleum jelly or a heavy zinc oxide ointment—along the belly midline and chest to create a physical barrier. Midges are tiny and simply cannot bite through a layer of grease.
➡ Upgrade Your Fly Spray: For a horse suffering from an intense allergic reaction, gentle, natural fly sprays (like citronella or essential oil blends) are rarely strong enough. You will generally need heavy-duty, long-lasting synthetic fly spray (such as permethrin) to keep biting midges away. Even at that, you will find that you will have to reapply it often.
➡ Adjust Turnout Schedules:Midges and mosquitoes are most active at dawn and dusk. Stabling your horse during these peak hours can significantly reduce bite exposure.
➡ Increase Airflow: Midges are weak flyers. Installing strong fans in your horse’s stall can create a physical air barrier that keeps them from landing. Be careful that the fan has a sealed motor to minimize the chance of the fan overheating and becoming a fire hazard.
➡ Manage the Environment:Eliminate standing water around the barn to reduce mosquito and midge breeding grounds, and treat or eradicate fire ant mounds in grazing areas.
➡ Provide Safe Scratching Stations: A horse with IBH will do almost anything to relieve the intense itch, often destroying fences or stall walls in the process—and risking serious injury from sharp wood or wire. Consider installing purpose-built scratching pads (like those used for cattle) on sturdy posts to provide a safe way for them to scratch.
◆︎ Treat Topically
Bites and welts can be highly irritating, painful, and intensely itchy. Providing topical relief is a kind first step to keeping your horse comfortable.
☛ Bathe Regularly: Wash your horse thoroughly with a gentle, hypoallergenic or oatmeal-based shampoo. This removes allergens from the coat, treats contact dermatitis, and washes away sweat, which actively attracts biting insects.
☛ Watch for Secondary Infections: The biggest complication of IBH isn't the allergy itself—it is the itch-scratch cycle. When a horse aggressively rubs its itchy skin, the skin breaks and opportunistic bacterial and fungal infection may occur. If the welts turn into weeping, crusty, or warm sores, you may be dealing with a secondary bacterial infection. This may require an antimicrobial scrub or a topical antibiotic.
☛ Apply Soothing Agents: After washing, dabbing the affected skin with pure witch hazel can be highly beneficial. Witch hazel is known to reduce localized inflammation and soothe itchiness. For severe scabbing, your veterinarian may also recommend specialized medicated shampoos or topical corticosteroid creams.
◆︎ Evaluate the Base Diet
Before adding targeted supplements, take a look at your horse's diet. Diets high in sugars and starches — such as traditional sweet feeds — can exacerbate systemic inflammation and put the immune system on high alert. Transitioning to a low sugar/starch diet may be helpful in managing inflammatory skin conditions.
◆︎ Supplements
Targeted nutritional supplements may help regulate the immune system. These are most effective when started prior to a full-blown inflammatory response. It’s easier to stop a runaway train before it runs away.
Supplement
Spirulina: Once your horse is accustomed to the smell and taste, the recommended serving size is 1/8 cup, twice a day. Or if you only go to the barn once per day, ¼ cup once a day.
Chondroitin sulfate: Recommended serving size is 5-10 grams, twice per day.
Quercetin: Recommended serving size is 5 grams, twice per day.
Turmeric: Recommended serving size is 2 grams, twice per day.
MSM: Recommended serving size is 10 grams, twice per day.
You may use these in combination with each other.
◆︎ Seek Veterinary Care
If your management and supplement remedies are not enough, be sure to involve your veterinarian.
- Rule Out Underlying Conditions: Work with your vet to discover any underlying issues that may make your horse susceptible to an exaggerated immune response. Untreated or undertreated conditions like Cushing’s disease (PPID), Insulin Resistance, or tick-borne diseases can weaken the immune system and make hives nearly impossible to control.
- Discuss Prescription Medications:Your vet may determine that prescription drugs are the most prudent course of action to break the itch cycle. This often includes antihistamines (such as hydroxyzine) or systemic corticosteroids (such as dexamethasone or prednisolone). Note: Your vet will carefully weigh the benefits of steroids against the potential risks, such as laminitis.
- Explore Immunotherapy: For severe, chronic cases of IBH, your veterinarian might recommend allergy testing followed by Allergen-Specific Immunotherapy (allergy shots), which slowly desensitizes your horse’s immune system to specific insect saliva over time.
◆︎ Be Persistent
Treating established hives is a bit like trying to put out a forest fire with a garden hose—it takes time, and results rarely occur overnight. Patience and persistence are your best tools, especially knowing that an allergic reaction is a runaway train inside the immune system.
We all want to do the very best for our horses. Take a deep breath, stick to your management routine, and work closely with your veterinary team to keep your horse comfortable this itchy season.
We do the best we can for our horses. Understanding our horse's needs is a part of that.
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Disclaimer: Statements regarding dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease or health condition.
©Joan Kulifay, MSc. 2026