Scratches in horses (mud fever): what causes it, how to care for it and when to call the vet

What are scratches in horses?

Scratches in horses is a skin reaction at the back of the pastern that vets call equine pastern dermatitis, and it is a description of what the skin looks like rather than a diagnosis with one cause. UC Davis describes pastern dermatitis as "inflammation of the skin on the back of the pastern(s)", and Purdue adds that it can affect the heel, the back of the pastern, the fetlock and occasionally the cannon bone. A 2013 review by Anthony Yu put it bluntly: pastern dermatitis "should be considered a syndrome, rather than a diagnosis." In other words, scratches tells you where the problem is and roughly what it looks like, and the cause still has to be found.

Scratches, mud fever, greasy heel, dew poisoning: one problem, many names

Scratches, mud fever, mud rash, greasy heel, cracked heels and dew poisoning are all names for pastern dermatitis in horses, a condition documented since the early 1800s. UC Davis lists all six names. "Scratches" is the usual word in the US, "mud fever" in the UK, and the British Horse Society also uses mud rash, greasy heels and cracked heels. World Horse Welfare notes that the term covers a wide range of skin conditions. A 2023 review from the University of Bern links the old names to stages: scratches, mud fever and mud rash to the mild form, and grease heel and dew poisoning to the wet, crusty form. So when someone at the barn talks about dew poisoning in horses, they usually mean the same condition at a weepier stage.

What do scratches look like?

Scratches on a horse's legs usually start as patchy red skin with oozing, crusts and small sores at the back of the pastern, followed by swelling of the lower leg; the skin can itch or be sore, and some horses go lame. That is the sequence UC Davis describes. The mud fever symptoms on the BHS list are much the same: scabs on the heels or lower legs, matted hair or bald patches with raw skin underneath, a creamy, white, yellow or green discharge between the skin and the scabs, and heat, pain and swelling in the lower leg. World Horse Welfare adds that in severe cases the skin may split open at the back of the leg, which is where the name cracked heels comes from, and that the horse may react when you press on or bend the leg.

A few details help when you look. Horse scabs on the legs are the most common sign: in a group of Swiss horses described by their owners, the Bern review reports crusts in 90% of horses, but lameness in only 3%. In feathered horses, the same review notes that a proper look at the skin is often impossible without clipping. And it doesn't always stay low: in its 2023 advice, Blue Cross writes that in extreme cases mud fever can spread up the legs and onto the belly.

Mild, weeping and chronic: how scratches can progress

The Bern review describes three forms of equine pastern dermatitis: a mild form, a wet and crusty (exudative) form, and a chronic thickened form seen mainly in draft horses. In the mild form the first signs are hair loss, dry scales and crusts with some pain or itching. As it progresses, the lesions start to weep and crust and often spread from the back of the heel upward and toward the front of the leg. The third, chronic proliferative form, with thickened, cracked and sometimes warty skin, belongs mostly to heavy, feathered breeds and is covered below under draft horses.

What causes scratches in horses?

No single cause has been proven: pastern dermatitis can be triggered by long exposure to wet and mud, mites, bacteria, allergies, drug reactions, fungi and sunlight damage to white legs. That list comes from UC Davis. The 2023 Bern review goes further: "Causality has not been demonstrated for specific infectious agents." What studies have found consistently is a link with Chorioptes mites and with an imbalance of the bacteria on the skin, but not with fungal infections. The review also lists conditions that can look similar, such as sarcoid, photosensitization, pemphigus foliaceus, sarcoidosis and habronematosis, and UC Davis names ringworm as a contagious cause to keep in mind. That is the practical reason to have a vet look before you treat.

Wet legs, mud and dirty bedding

Long exposure to moisture, from wet bedding or muddy pastures, seems to be a common cause of mud fever in horses or at least keeps it going, although the evidence on rain itself is inconclusive. UC Davis calls extended exposure to moisture "a common cause or perpetuating factor", and the BHS explains that wet conditions soften the skin and mud rubs against it, letting bacteria in, which is why mud fever is common in winter. The BHS lists these risks:

• standing in mud or wet conditions for long periods;
• standing in dirty bedding;
• washing the legs regularly, especially without drying them afterward;
• broken or damaged skin from a wound, such as an overreach injury, that lets bacteria in.

The research is more cautious. The Bern review says the evidence for rainfall and humidity is inconclusive, and a one-year study of six stallions found no clear link between lesion severity and rainfall, with lesions getting worse in autumn and early spring; the authors note the group was too small for firm conclusions.

Mites in feathered legs

Chorioptes leg mites are common in heavily feathered horses and make them itch, stamp and break the skin, which can look like or lead to scratches. The BHS writes that horses with thick feathers are more at risk of leg mites and stamp their legs because they itch. Merck calls leg mange the most common form of mange in horses, mostly in draft breeds and most often on the hind legs, with signs that lessen in summer and return with cold weather. Blue Cross adds flakes of dry skin in the feathers, often called walking dandruff, and excessive stamping. In a 2025 study of 156 Belgian draft horses, 92.31% had Chorioptes bovis mites, while none of 142 Belgian warmbloods had them. Stamping and itchy legs are a different problem from sweet itch, and the BHS advice is simple: if you suspect mites, speak to your vet.

White legs and sunlight

White legs with pink skin are more easily damaged by sun, and two conditions linked to sunlight, photosensitization and pastern vasculitis, can look like mud fever without any mud involved. Purdue notes that unpigmented skin is more susceptible to sun damage, chafing and abrasions. In photosensitization, substances in the skin react to sunlight; Merck says the affected areas are usually lightly pigmented or have little hair, and that in horses it often involves impaired liver function, for example after grazing plants that are toxic to the liver. If your vet suspects that, a blood chemistry panel can look for liver disease, according to the Bern review.

The second condition, pastern leukocytoclastic vasculitis, affects mostly legs with white markings, with painful, red, oozing patches and tightly adherent crusts. The Bern review calls it possibly made worse by light and gives it a guarded prognosis. A 2013 study of 20 horses found the lesions mainly on the inner and outer sides of unpigmented legs, a poor response to treatment, and no underlying cause. UC Davis notes that in some cases avoiding sun exposure may be helpful.

Is it rain rot on the legs?

Sometimes: Dermatophilus congolensis, the bacterium behind rain rot, can infect the lower legs, but a small 2018 study found it in only one of 15 horses with pastern dermatitis. Merck's professional manual notes that persistent wetting of the pasterns can lead to lower limb infection with this organism, and the BHS says rain scald can be caused by the same bacteria as mud fever. But in the 2018 study from the southern US, the PCR test found D. congolensis in one non-feathered horse out of 15 and in none of the feathered ones, while four of the 15, all feathered, had Chorioptes mites. The Bern review notes that those samples were swabs or crusts rather than biopsies. Our guide to rain rot in horses covers the version on the back and rump.

Draft horses and chronic progressive lymphedema

In draft horses, severe and lasting leg lesions can be chronic progressive lymphedema (CPL), a lymphatic disease with thickened skin, folds and nodules that is incurable and needs lifelong management. A 2023 review describes CPL as increased skin thickness and fibrosis with skinfolds, nodules and ulcers on the lower legs, with a prevalence of up to 85.86% in Belgian draft horses. UC Davis points out that pastern dermatitis is not the same disease as CPL, and the Bern review describes CPL as a distinct disorder of the lymphatic system while counting it among the severe forms seen in cob and draft types. Mites are part of the picture: in the 2025 Belgian study, 80.77% of 156 draft horses showed signs of CPL and 92.31% carried Chorioptes mites.

Which horses get scratches?

Any horse can get scratches, but it is most common in draft breeds and horses with heavy feathering, and white legs, thin skin, age and a weakened immune system add to the risk. UC Davis names draft breeds and others with heavy feathering that trap moisture. The BHS adds the pink skin under white markings, thin-skinned breeds such as Thoroughbreds and Arabs, and a weakened immune system, for example in a horse with Cushing's disease, in which mud fever can also be harder to treat.

The Bern review adds some nuance from the studies: white legs were affected more often in lighter breeds such as warmbloods, but not in heavy German draft horses, severity increased with age in drafts, and males of heavy draft breeds were more susceptible to the severe forms. In lighter breeds, mild to moderate forms are the rule; the severe forms, including CPL, are seen in cob and draft types. We found no reliable figure for how common scratches is across all horses.

Are scratches contagious?

It depends on the cause: the BHS and Blue Cross call ordinary mud fever non-contagious, but mites, ringworm and some rarer infections behind pastern dermatitis do spread between horses. The BHS says mud fever doesn't spread from one horse to another or to people, and Blue Cross also calls it non-contagious. Other sources are more careful:

The Finnish outbreaks are exceptions, but they show that what looks like mud fever can travel through a barn: in a new outbreak in early 2025, researchers found the virus's DNA on grooming tools, stall surfaces, bedding and people's hands. PetMD, a commercial pet health site, also says scratches can spread to another horse through shared grooming equipment or direct contact. Since you can't tell the cause by looking, Purdue's advice is simple: don't share boots between horses. PetMD's point about shared grooming equipment, and the virus the Finnish researchers found on grooming tools, apply to brushes in the same way. Tell your vet whether other horses on the yard have it, because the Bern review lists the status of companion horses among the history a vet needs.

How to treat scratches in horses

Scratches treatment in horses starts with finding the cause, so the BHS advises calling your vet as soon as you suspect mud fever; meanwhile, a clean, dry environment and gentle handling of the skin are what the care guides from Purdue, the BHS, World Horse Welfare and UC Davis all advise. The BHS wants the vet involved early for an accurate diagnosis, and World Horse Welfare says that if in doubt you should confirm it is mud fever before starting any treatment. Once your vet has made a diagnosis and a plan, the BHS adds, you can usually manage the condition yourself. Mites, sun damage and vasculitis each need something different, and the Bern review admits that recommendations on medical treatment are still largely empirical, which means no cream or routine has been shown in trials to work best.

A Swiss owner study by the same Bern group shows how easily it goes the other way: 69% of treatment decisions were made without a vet, which made the underlying cause harder to find and the treatment often longer.

What you can safely do today

Until your vet has seen the legs, keep the horse in a clean, dry place, leave the scabs alone, keep wraps that hold moisture off the sore skin, don't turn out in bandages, and keep boots and brushes to one horse. Clipping is not on this list: the BHS places it after your vet's diagnosis, and it can be painful. These steps come straight from the sources:

1. Get the legs out of the wet. Purdue calls a dry, clean environment the primary defense to allow healing: off wet pasture and into a clean, dry stall. Purdue prefers large, fluffy shavings to milled ones, which hold more moisture.
2. Don't pick the scabs. Purdue's rule of thumb is "Don't scratch scratches", and the BHS says scabs shouldn't be forcibly removed unless your vet advises it. Removing scabs or clipping a sore leg can hurt enough that the BHS, World Horse Welfare and the Bern review all mention sedation.
3. Be gentle with the skin. Purdue warns against rough scrubbing and harsh chemicals. If your vet advises washing, World Horse Welfare says to use warm water, never cold, and never to put undiluted disinfectant on the skin. Afterward, the BHS says to pat the leg dry with a clean towel.
4. No wet wraps and no bandages in the field. Purdue says not to use wraps or boots that hold moisture around the sore areas, and World Horse Welfare says never to turn a horse out in bandages, because they can easily cause rubs or injuries. Bandages in the stable are a different matter: in the treatment plan that follows your vet's diagnosis, the BHS says stable bandages on dry legs can help keep them clean, give support and reduce swelling.
5. One horse, one set of kit. Purdue says not to share boots between horses, and PetMD says scratches can spread through shared grooming equipment, so boots and brushes stay with the affected horse.

What your vet may check

To find the cause, your vet may take skin scrapings for mites, a biopsy, bacterial and fungal cultures, blood tests or X-rays, and will ask when it started and what you have already used. UC Davis lists biopsy, cultures, skin scrapings for Chorioptes mites and radiographs to rule out other causes of lameness. The BHS adds a blood test in severe cases and a swab if mud fever isn't clearing up. The Bern review notes that in feathered horses the skin often can't be examined properly without clipping, and that samples for the lab are best taken, if possible, before the leg is cleaned. In severe cases clipping can be very painful, and World Horse Welfare says it may need to be done under sedation by your vet. Once your vet has made a diagnosis and a plan, the BHS says that in a horse with thick feathers you may need to clip the hair carefully yourself so the skin can be cleaned and treated, and Purdue adds that clipping should not scrape or break the skin. The history matters too: UC Davis says the season when signs first appeared, plus "any use of topical medications or home remedies", can aid the diagnosis, and the Bern review adds previous treatments and how they went.

Which cream is best for mud fever?

No study shows that one cream works best for mud fever, so the cream is your vet's choice, and any barrier cream goes only on clean, dry skin. The Bern review notes that Swiss owners used over 50 different ingredients and that treatment advice remains largely empirical; zinc oxide is one of the wound-healing ingredients it mentions in such creams. The BHS warns that a barrier cream on skin that isn't dry and clean gives bacteria a perfect place to grow between skin and cream, and World Horse Welfare says a thick barrier cream used as a preventative before turnout should only go on clean, dry skin and not when lesions are present. Once a horse is being treated, the same page advises continuing a barrier cream during turnout until the area has healed completely, and says that you should "avoid thick oily ointments" because these bacteria like airless conditions. Purdue does mention a zinc oxide based cream, applied only to dry affected areas, as something that may help soften scabs and provide a moisture barrier. We found no study showing that one cream, nappy or diaper cream, mouthwash, natural remedy or home recipe works better than another. The Bern review describes three original studies of treatments applied to the skin, including two small trials against a placebo, one of them with a plant essential oil, in which lesion scores improved in the treated horses; it still calls treatment recommendations largely empirical and asks for adequately powered, controlled trials, so none of these studies tells you which product to use.

When to call the vet about scratches or mud fever

The BHS advises calling your vet as soon as you suspect mud fever, and Purdue and the BHS name severe lameness, deep wounds with swelling, heat or discharge, any swelling of the leg and treatment that isn't working as specific reasons to call. These are the signs that the sources themselves tie to calling or speaking to your vet:

The other signs in this guide, such as green discharge, skin splitting at the back of the leg or a horse that reacts when you press on or bend the leg, are described by the BHS and World Horse Welfare as signs of mud fever rather than as separate reasons to call; they fall under the BHS rule to call as soon as you suspect it, and World Horse Welfare's advice to call your vet if in doubt. Sores mainly on white legs are a case in point: the Bern review describes pastern vasculitis as affecting predominantly but not exclusively legs with white markings, and as something a vet confirms with a biopsy. The BHS also notes that mud fever can be harder to treat in a horse with a weakened immune system, such as one with Cushing's disease.

Swelling deserves particular attention, because the BHS warns that untreated mud fever can lead to cellulitis and even lymphangitis, bacterial infections in the lower leg that often affect one leg at a time. The Bern review notes that lameness appears in sensitive horses or severe cases, especially when cellulitis develops, so mud fever can make a horse lame and can cause swelling. Many owners wait too long: in the Swiss owner study, 32% of horses only saw a vet after they showed pain or lameness. Our guide to contacting your vet covers what to have ready for the call.

How long does it take for scratches to heal on horses?

We found no veterinary body or study that gives a healing time for scratches in days or weeks, and only PetMD, a commercial pet health site, offers one: most cases recognized and treated early resolve within a few weeks. What the veterinary sources do say, mainly the Bern group and a review of chronic lymphedema in draft horses, is this: mild to moderate cases usually do well once the cause is clear, scratches often comes back, and the severe chronic form in draft horses can't be cured. The Bern review gives the prognosis as usually good in mild to moderate cases with adequate, consistent treatment, provided vasculitis and other causes have been ruled out. UC Davis says that early, accurate diagnosis and the right treatment give the best results, and that without it lesions can spread to the cannon area and secondary bacterial infections are common. World Horse Welfare agrees that treating mud fever as soon as you spot it increases the chance of success. The PetMD figure, from a commercial site rather than a veterinary body, reads in full: "If recognized and treated early, most cases of scratches in horses resolve within a few weeks."

It often comes back: in one Swiss owner study, recruited through social media, 62% of horses had shown signs at least four times in their lives. For the severe chronic form, the Bern review says plainly that severe pastern dermatitis and CPL are incurable, although lifelong management may slow it down, and that treating mites in feathered horses eased their discomfort but didn't reduce the severity of the skin disease. A dated note of each episode, with what was used and how it went, is exactly the history your vet will ask for the next time.

Can you ride a horse with mud fever?

No veterinary source we checked gives a rule on riding a horse with ordinary mud fever or scratches, so the decision belongs to your vet, and a severely lame or swollen leg is in any case a reason to call. The BHS, World Horse Welfare, Blue Cross, UC Davis, Purdue and the Bern review give no rule for ordinary mud fever; the Bern review mentions controlled exercise only as part of managing the severe chronic form in draft horses. What the sources do give are the reasons to call in the table above, such as severe lameness and any swelling of the leg. Ask your vet about work at the same visit where you get the diagnosis.

How to prevent scratches and mud fever

To prevent mud fever in horses, give them somewhere dry to stand every day, fix the muddy spots at gates and water troughs, let mud dry before you brush it off, keep bedding clean and dry, and check the legs daily. The BHS, Purdue, UC Davis and World Horse Welfare give these steps:

• A dry place every day. The BHS asks for somewhere dry to stand for at least part of the day.
• Fix the worst mud. Rotate fields, put hardcore down where horses gather, such as gateways and water troughs, and fence off very muddy areas (BHS); Purdue suggests filling in muddy areas around gates. Our guide to autumn grazing and the autumn care checklist cover the field side.
• Don't hose muddy legs. The BHS advises against washing the legs when you bring a horse in: wait until the mud is dry and brush it off with a soft brush. Purdue says to dry the legs before putting the horse in a stall.
• Watch the dew. Purdue advises avoiding early morning turnout when there is heavy dew or frost on the ground.
• Clean, dry bedding. UC Davis calls stable hygiene with clean, dry bedding essential, and suggests keeping the hair on the lower legs clipped.
• Turnout boots that fit. The BHS says boots designed for turnout can help if they fit well enough to avoid rubs, and World Horse Welfare says they may offer some protection. A barrier cream before turnout belongs only on clean, dry skin.
• Deal with what's underneath. The BHS advises treating underlying conditions such as mites, fungal infections or wounds.
• Look every day. World Horse Welfare and the BHS advise checking the legs daily, and Purdue calls early detection the best medicine.

For draft horses with CPL, a 2023 study of Rhenish German draft horses found that pasture and clean bedding were linked to lower scores, and hay silage and concentrates in winter to higher ones; that is an association from one study, not proof. And in fairness to all the advice above, the Bern review notes that the value of these management steps has not been investigated. They are sensible and cheap, and they come from experience rather than trials. For wet days when turnout is on the line, see our guide to rugs and weather.