While grooming, you find a bald patch, a row of small scabs on the back, or a lump that wasn't there yesterday. Skin problems are one of the most common sources of doubt for horse owners, partly because very different causes can look the same at a glance. This guide helps you tell the best-known patterns apart — where they sit, how they feel, and what they're likely to be. The diagnosis itself remains the vet's job.
First, Look and Feel
Before you start guessing, gather a few details. They make the difference between "just a spot" and a recognizable pattern, and they'll help the vet later on the phone.
- Where is it? Back and croup, lower legs, head, belly, or groin — the location often already points in a direction.
- How does it feel? Moist or dry, warm, painful to the touch, or not. Are there loose scabs, or is it stuck fast to the skin?
- Does it itch? Does the horse rub against fences and stall walls, or does it leave the spot alone?
- How fast did it appear? Overnight, or did it grow slowly over weeks?
- How many horses? Just one animal, or is the whole yard affected — the latter points to something contagious.
Take a few photos in good light and note the date. For a spot that's changing, how it develops over time is often the most important piece of information.
Scabs and Bald Patches: The Wet Presentations
Most everyday skin problems revolve around moisture, scabs, and hair loss. These are the patterns you'll run into most often.
- Rain rot (rain scald). Rows of small scabs on the back, croup, and rump, often after a long wet spell. Lift a scab and a small tuft of hair comes with it, leaving a bald, sometimes slightly raw spot behind (so-called "paintbrush" lesions). Caused by a bacterium that thrives in a damp coat.
- Mud fever (scratches). Scabs, cracks, and swelling low on the pastern and heel bulbs, on the back of the lower leg. Common on white legs and in wet, muddy conditions. Can become painful and make the leg swell up.
- Ringworm. Round, bald patches that expand, often in the saddle and girth area or wherever horses touch each other. Highly contagious between horses and via shared equipment, and can also spread to people. With multiple affected animals, or any doubt, this is one for the vet.
- Sweet itch (summer itch). Intense itching at the mane, tail base, and belly line, with bald, rubbed-raw patches. Mainly active during insect season and caused by a hypersensitivity to the bite of midges (small biting gnats). Returns every year in sensitive horses.
| Pattern | Location | Itch | Typical Circumstances |
|---|---|---|---|
| Rain rot | Back, croup, rump | Little | Long spells of wet weather |
| Mud fever | Pastern, heel bulbs | Sometimes | Mud, wet legs |
| Ringworm | Saddle/girth area, head | Variable | Contact between horses, shared tack |
| Sweet itch | Mane, tail, belly | Intense | Insect season, dusk |
Lumps Under the Skin
Not every lump is cause for concern, but the pattern determines how urgent it is.
- Hives (urticaria). Suddenly a lot of soft, round bumps over a large part of the body, often with itching. Usually an allergic reaction to something — an insect bite, feed, a new product. Often gone within a day, but with breathing difficulty or facial swelling it's an emergency.
- Insect bites. Individual, warm bumps, sometimes with a small central point, in spots the horse can't easily reach. Usually harmless and resolve on their own.
- Summer sores (habronemiasis). Stubborn, non-healing wounds with "grainy" red tissue bulging out, often during the warm season. They heal poorly without treatment and need to be seen by a vet.
Sarcoids: The Best-Known Skin Tumor
A sarcoid is the most common skin tumor in horses. It's benign in the sense that it doesn't spread to other organs, but it keeps growing locally, can come back after removal, and responds poorly to a "wait and see" approach. Precisely because sarcoids vary so much in appearance, they're easily mistaken for a wart, a scar, or a non-healing wound.
Common presentations:
- A flat, bald, flaky patch that seems stable for a long time.
- One or more firm, wart-like nodules.
- A larger, sometimes pendulous mass, sometimes with an open, non-healing surface.
Preferred sites are the head (around the eyes, ears, corners of the mouth), the belly and groin, and places where a wound sat before. Important: never prick, cut, or treat a suspected sarcoid yourself, and don't apply unknown ointments to it. Clumsy intervention can turn a quiet sarcoid aggressive. Have any suspicious, growing, or non-healing spot assessed by the vet; they'll determine whether and how it needs to be treated.
General Approach and Hygiene
Before the cause is clear, a few sensible basic rules apply — without playing doctor yourself.
- Keep the skin dry and clean. For the wet presentations, a dry, sheltered spot, a clean coat, and air reaching the skin often help a great deal. Don't scrub endlessly at painful scabs.
- Isolate if you suspect infection. If you suspect ringworm or another contagious condition, use separate grooming kit, rugs, and saddle pads, and wash your hands after handling. Don't share between horses.
- Control insects for itching. With sweet itch and insect pressure, a fly rug, stabling in good time around dusk, and a manure-light environment all help a lot.
- Don't change everything at once. With hives or a suspected allergy, it helps to note down what recently changed in feed, tack, or products.
- No human or unknown remedies. What works for you or another animal can irritate horse skin or muddy a diagnosis.
When to Call the Vet
Call the same day, or right away, for:
- Rapid swelling of the head, eyelids, or airways, or difficulty breathing — a severe allergic reaction is an emergency.
- Fever, listlessness, or not wanting to eat alongside the skin problem — there may be more going on than the skin alone.
- An open, non-healing, or growing spot, or a lump that changes in shape or size — have this assessed before you try anything.
- Intense itching that makes the horse rub itself raw, or painful, cracked-open mud fever with a swollen leg.
- Multiple horses with the same spots — then you'll want to know quickly whether it's contagious.
For a small, stable, painless spot without itching, you can monitor and photograph it for a few days. If it changes, spreads, or you're unsure, call anyway. For a reliable diagnosis, the vet sometimes needs a skin scraping, a hair sample, or a biopsy — something you can't substitute by eye.
In Short
Look carefully first: where it is, how it feels, whether it itches, and whether it's one horse or the whole yard. The wet presentations (rain rot, mud fever, ringworm, sweet itch) revolve around moisture, scabs, and itching, and are usually recognizable by location and circumstance. Lumps range from harmless insect bites to hives and non-healing summer sores. A growing, non-healing, or changing spot could be a sarcoid — never prick or apply ointment to one yourself. Keep the skin clean and dry, isolate equipment if you suspect infection, and call the vet for rapid swelling, fever, a changing spot, or multiple affected horses. For the diagnosis, the vet remains the right source, always.
See also: Daily horse care: the basic routine · Recognizing lameness in horses · Terms in the glossary