Last updated: April 18, 2026
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Veterinary disclaimer: Hair loss in horses can indicate infectious, parasitic, hormonal, or nutritional conditions — some of which are contagious to other horses or to humans. This guide is for educational purposes. If you are unsure of the cause, or if hair loss is spreading, accompanied by itching, skin changes, or behavioral changes, consult a licensed veterinarian for diagnosis and treatment.
When my granddaughter’s horse began shedding hair in noticeable patches — bare skin where there should have been a healthy coat — it was immediately clear something was wrong. Seeing bald patches appear on a horse you care for is alarming, and the cause isn’t always obvious.
In older horses, it can also be a sign of Cushing’s disease. The key is how the skin looks under the missing hair. Knowing how to tell the difference, and when to stop treating at home and call the vet, is what this guide covers.
Most cases fall into a few common categories — infections, parasites, allergies, or hormonal disease.
Most common causes of a horse losing hair in patches:
- Ringworm — circular patches of hair loss with scaly or crusty skin; fungal, not a worm; contagious to humans and other horses
- Rain rot (rain scald) — matted tufts of hair that pull away, leaving moist raw skin underneath; bacterial; worsened by wet weather
- Sweet itch — intense itching along the mane and tail base caused by Culicoides midge bites; horse rubs until bald
- Mites (mange) — intense itching, crusty or thickened skin, most common on the lower legs in feathered breeds
- Lice — visible on the coat; rubbing and itching concentrated on the neck, mane base, and flanks
- Cushing’s disease (PPID) — abnormal coat that fails to shed, patchy growth, often in older horses; requires veterinary diagnosis
- Nutritional deficiency — diffuse or patchy hair loss without obvious skin irritation; often accompanied by poor coat condition overall
The two most commonly confused causes are ringworm and rain rot. Here’s how to tell them apart quickly:
| Feature | Ringworm | Rain Rot |
|---|---|---|
| Skin | Dry, scaly, circular patches | Wet, raw skin under scabs |
| Hair loss | Clean-edged bald spots | Matted tufts that lift off |
| Contagious | Humans + horses | Horses only |
| Cause | Fungal infection | Bacterial infection |
Table of Contents
Normal Shedding vs. Abnormal Hair Loss
Every horse sheds twice a year — a heavier shed in spring as the winter coat releases, and a lighter transition in fall. During these periods, hair comes out in large amounts when groomed, the coat looks rough and uneven, and patches of new growth may appear at different lengths. This is entirely normal and requires no treatment beyond regular grooming to help the process along.
Abnormal hair loss is different. The signs that distinguish a problem from normal shedding are bald patches with visible skin, hair loss concentrated in specific areas rather than distributed across the body, associated skin changes like scaling, crusting, or redness, and itching or rubbing that the horse wasn’t doing before. If you’re seeing any combination of these alongside hair loss, it’s not seasonal shedding — something is causing it.
Ringworm
Despite the name, ringworm is a fungal infection — not a worm. It’s caused by dermatophyte fungi and is one of the most common causes of patchy hair loss in horses. The classic presentation is circular or roughly circular bald patches, often with scaly, flaky, or crusty skin at the edges. The patches may start small and expand, and multiple patches often appear around the same time. Common sites are the saddle area, girth line, and face — places where tack contacts the skin or where grooming equipment is shared.
Treatment is antifungal — typically a topical wash containing enilconazole or miconazole applied to the affected areas. In widespread cases, systemic antifungal treatment may be needed and requires veterinary prescription. The environment also needs to be addressed: disinfect stalls, tack, and shared equipment, because the fungal spores are hardy and can survive for months on surfaces. Good grooming hygiene practices — separate brushes and equipment per horse — are the most effective prevention. Most cases resolve within four to six weeks with consistent treatment, but recurrence is common if contaminated equipment is not properly cleaned.
Rain Rot (Rain Scald)
Rain rot is caused by the bacterium Dermatophilus congolensis and is the most common skin infection in horses kept in wet conditions. It presents as matted tufts of hair that lift away from the skin in small clumps, often with a crust or scab attached to the base of each tuft. When the tufts are removed, the skin underneath is raw, moist, and sometimes bleeding. The back, hindquarters, and topline are the most commonly affected areas — the places where rain runs down and sits.
The condition is worsened by prolonged exposure to moisture combined with minor skin abrasions that let the bacteria in. A horse standing in a wet paddock or under a leaky shelter with a compromised skin barrier is the ideal environment for rain rot to develop. Treatment involves removing the scabs (which harbor the bacteria), washing with an antiseptic shampoo, and — critically — drying the horse and keeping it out of wet conditions. Whether you can ride a horse with rain rot depends on the severity and location of the lesions. In severe cases or when the infection has penetrated deeper, antibiotics from a veterinarian are needed. Preventing recurrence means addressing the environmental factors that cause it.
Sweet Itch (Insect Hypersensitivity)
Sweet itch is an allergic skin reaction to the saliva of Culicoides midges — tiny biting insects that are most active at dawn and dusk and near standing water. Horses with sweet itch develop intense, persistent itching concentrated along the mane, tail base, and sometimes the belly and face. The itching is so severe that affected horses rub themselves raw against fence posts, trees, and stall walls, creating bald patches and open wounds. The skin in these areas becomes thickened, scaly, and permanently scarred in chronic cases.
Sweet itch is a hypersensitivity reaction, which means there is no cure — only management. The goal is reducing midge exposure and controlling the itch response. Effective management includes stabling the horse during midge activity periods (dawn and dusk), using fly rugs with full neck and belly coverage, applying midge-specific repellents, and in severe cases, veterinary treatment with antihistamines or corticosteroids to control the allergic response. Horses with sweet itch tend to be worse in warm, humid weather and in areas near water.
Mites and Mange
Several mite species affect horses, each causing slightly different presentations. Chorioptic mites are the most common and primarily affect the lower legs, causing itching, stomping, and skin changes around the fetlocks and pasterns — a condition called chorioptic mange. The skin becomes crusty, thickened, and scaly, and hair loss in the affected area follows the inflammation. Feathered breeds like Clydesdales and Shires are particularly susceptible because mites thrive in the warm, moist environment beneath heavy feathering.
Sarcoptic mites burrow into the skin and cause more severe, widespread disease with intense itching and secondary infections. Psoroptic mites live on the skin surface and cause itching, hair loss, and scab formation. All forms of mange require veterinary diagnosis — mites are often too small to see with the naked eye, and confirming which species is present (via skin scraping) is important for selecting the right treatment. Treatment typically involves topical or injectable antiparasitic drugs and thorough cleaning of the environment and equipment. See the guide to mites, lice, and parasites in horses for more detail on each type.
Lice
Lice infestations in horses are more common in winter when horses are in closer contact and wearing rugs. There are two types: biting lice (which feed on skin debris) and sucking lice (which feed on blood). Both cause itching that leads to rubbing and subsequent hair loss, concentrated most often around the mane base, neck, flanks, and tail head. Unlike mites, lice are visible to the naked eye if you part the hair and look closely — small, slow-moving insects clinging to hair shafts, along with their eggs (nits).
Treatment is straightforward — topical insecticide products in powder, spray, or shampoo form applied to the affected areas, repeated at the appropriate interval to catch hatching nits. All horses in contact with an infested horse should be treated simultaneously. Equipment, rugs, and bedding should be cleaned or replaced to prevent re-infestation. Lice are host-specific — horse lice do not transfer to humans or dogs.
Cushing’s Disease (PPID)
Pituitary Pars Intermedia Dysfunction (PPID), commonly called Cushing’s disease, is a hormonal disorder most commonly seen in horses over fifteen years old. The most recognizable sign is a long, curly, and often patchy coat that fails to shed normally — a horse in midsummer that still has a shaggy winter coat is a classic presentation. Other signs include patchy hair loss or abnormal coat texture, increased water intake and urination, a pot-bellied appearance, muscle wasting over the topline, and increased susceptibility to infections.
Cushing’s disease requires veterinary diagnosis through a blood test measuring ACTH levels. It cannot be treated at home and should not be managed with supplements alone. The standard medication is pergolide, which manages the hormonal imbalance effectively and significantly improves quality of life in affected horses. If your older horse has a coat that doesn’t shed properly alongside any of the other signs above, a veterinary examination is the right next step — early diagnosis and treatment make a meaningful difference in outcomes. Cushing’s horses are also more susceptible to laminitis, which adds urgency to getting the hormonal imbalance controlled.
Nutritional Deficiency
Poor nutrition can cause diffuse hair loss or a generally poor coat quality that includes thin, sparse patches. The most relevant nutrients for coat and hair health are protein (particularly the amino acids methionine and lysine), zinc, copper, and biotin. A horse on low-quality forage without appropriate supplementation may develop a coat that looks dull, breaks easily, and fails to grow normally. Unlike the infectious and parasitic causes above, nutritional deficiency hair loss tends to be distributed rather than in isolated circular patches, and the skin underneath is usually normal in appearance.
Addressing nutritional deficiency starts with a forage analysis to understand what the base diet is actually providing. From there, targeted supplementation based on identified gaps is more effective than adding a broad-spectrum supplement and hoping it covers the problem. Work with your veterinarian or an equine nutritionist rather than guessing — over-supplementing certain minerals like selenium can cause hair loss in its own right, so more is not always better. For a detailed look at the role of nutrition in coat quality, see the guide to horse coat nutrition for a shiny, healthy coat.
How to Tell Why Your Horse Is Losing Hair (Quick Diagnosis Table)
| Cause | Appearance | Common Location | Contagious? | Vet Required? |
|---|---|---|---|---|
| Ringworm | Circular bald patches, scaly edges | Saddle area, girth, face | Yes — horses and humans | Advisable; required if widespread |
| Rain rot | Matted hair tufts, raw skin beneath | Back, hindquarters, topline | Yes — horses | If severe or not responding |
| Sweet itch | Rubbed bald patches, thickened skin | Mane, tail base, belly | No | For corticosteroids if severe |
| Chorioptic mites | Crusty, thickened skin; stomping | Lower legs, fetlocks | Yes — horses | Yes — skin scraping for diagnosis |
| Lice | Visible insects; intense rubbing | Mane, neck, flanks, tail head | Yes — horses only | No — OTC treatment available |
| Cushing’s (PPID) | Patchy, curly, non-shedding coat | Full body; topline muscle loss | No | Yes — diagnosis and Rx required |
| Nutritional deficiency | Diffuse poor coat, sparse patches | Full body; no isolated patches | No | For forage analysis and plan |
FAQs About Horses Losing Hair in Patches
Why is my horse losing hair in patches?
The most common causes are ringworm (a fungal infection), rain rot (a bacterial skin infection), sweet itch (allergic reaction to midge bites), mites, or lice. In older horses, Cushing’s disease (PPID) can cause an abnormal coat that fails to shed properly and appears patchy. Nutritional deficiency can also cause poor coat quality and sparse patches. The condition of the skin beneath the missing hair — dry and scaly, wet and raw, or thickened and crusty — helps narrow down the cause.
Is ringworm in horses dangerous to humans?
Yes. Ringworm (a fungal infection, not a worm) is contagious to humans and presents as a circular, itchy rash on the skin. Anyone handling a horse with suspected ringworm should wear gloves, wash hands thoroughly afterward, and disinfect grooming tools and tack. If a person develops a skin rash after contact with an affected horse, they should see a doctor.
What does rain rot look like on a horse?
Rain rot presents as matted tufts of hair that lift away from the skin, often with a scab or crust at the base of each tuft. When the tufts are removed, the skin underneath is raw, moist, and sometimes bleeding. It most commonly appears on the back, hindquarters, and topline — areas where rain runs down and sits. It is caused by the bacterium Dermatophilus congolensis and is worsened by prolonged wet conditions.
How do I know if my horse has mites?
Chorioptic mites — the most common type — typically affect the lower legs, causing intense itching, stomping, and crusty or thickened skin around the fetlocks and pasterns. The mites themselves are too small to see without magnification. A definitive diagnosis requires a veterinary skin scraping. Heavily feathered breeds are most susceptible because mites thrive under the warm, moist conditions beneath dense leg hair.
Can Cushing’s disease cause hair loss in horses?
Yes. Cushing’s disease (PPID) commonly causes an abnormal coat that fails to shed seasonally — a horse in summer that still carries a long, curly, or shaggy coat is a classic sign. The coat may also appear patchy or uneven in texture. Cushing’s primarily affects horses over 15 years old and requires veterinary diagnosis through a blood test. It is managed with daily medication (pergolide) and is not treatable at home.
What is sweet itch in horses?
Sweet itch is an allergic skin reaction to the bites of Culicoides midges. Affected horses develop intense itching along the mane, tail base, and sometimes belly and face, rubbing themselves raw against surfaces. The bald, thickened patches that result are a direct consequence of the rubbing rather than a direct effect of the midge bite. There is no cure — management focuses on reducing midge exposure through stabling at dawn and dusk, protective fly rugs, and veterinary antihistamines or corticosteroids in severe cases.
How do I treat a horse with hair loss?
Treatment depends on the cause. Ringworm requires antifungal wash and equipment disinfection. Rain rot requires scab removal, antiseptic shampoo, and drying the horse. Sweet itch requires midge management and protective clothing. Mites require veterinary diagnosis and antiparasitic treatment. Lice respond to topical insecticide products. Cushing’s disease requires veterinary diagnosis and daily medication. Nutritional deficiency requires forage analysis and targeted supplementation. Do not treat before identifying the cause — different conditions require different approaches.
Can nutritional deficiency cause patchy hair loss in horses?
Yes, though nutritional deficiency tends to cause diffuse coat thinning and poor hair quality rather than discrete circular bald patches. Key nutrients for coat health include protein (especially methionine and lysine), zinc, copper, and biotin. A forage analysis is the most accurate way to identify gaps. Work with a veterinarian or equine nutritionist rather than adding broad-spectrum supplements without knowing what the diet is actually missing.
When should I call the vet about my horse losing hair?
Call your vet if the hair loss is spreading rapidly, if you cannot identify the cause, if the skin beneath is severely inflamed or infected, if the horse is showing signs of systemic illness (weight loss, lethargy, increased thirst), or if the horse is older and the coat is not shedding normally. Ringworm, mange, and Cushing’s disease all require veterinary involvement for proper diagnosis or prescription treatment.
- Check the skin first — dry and circular points to ringworm; wet and matted points to rain rot; crusty lower legs point to mites. The skin condition underneath the missing hair is your best diagnostic clue
- Ringworm and rain rot are the most common causes — both are infectious, both spread through contact and equipment, and both respond well to appropriate treatment started early
- Ringworm is contagious to humans — wear gloves and disinfect equipment whenever ringworm is suspected
- Sweet itch has no cure — management through midge exposure reduction is the only effective approach
- Cushing’s disease in older horses requires veterinary diagnosis — a non-shedding, patchy coat in a horse over 15 years old warrants a blood test, not a grooming change
- Don’t treat before identifying the cause — the wrong treatment wastes time and can worsen some conditions
- Call the vet when hair loss is spreading, when you can’t identify the cause, or when any signs of systemic illness accompany the coat changes
For related horse health topics, see the guides on common horse diseases and their symptoms, horse coat nutrition, and mites, lice, and parasites in horses.
About Miles Henry
Racehorse Owner & Author | 30+ Years in Thoroughbred Racing
Miles Henry (legal name: William Bradley) is a professional horseman based in Folsom, Louisiana. He holds Louisiana Racing License #67012 and has spent over three decades managing Thoroughbreds at premier tracks including Fair Grounds, Delta Downs, and Evangeline Downs.
Expertise & Hands-On Experience: Beyond the track, Miles has decades of experience in specialized equine care, covering everything from hoof health and nutrition to training protocols for Quarter Horses, Friesians, and Paints. Every guide on Horse Racing Sense is rooted in this “boots-on-the-ground” perspective.
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