What Is Scratches in Horses: Causes and Treatment

Scratches is not a single disease but a syndrome: a catch-all term for inflamed, crusted, sometimes oozing skin on the lower legs of horses, most commonly around the pastern and heel bulbs. Veterinary literature calls it equine pastern dermatitis (EPD), though horse owners know it by a long list of barn names including mud fever, greasy heel, and cracked heels. Because multiple causes can produce the same angry-looking skin, effective treatment depends on figuring out which triggers are at work in a particular horse rather than reaching for a one-size-fits-all remedy.

A Syndrome, Not a Diagnosis

The most important thing to understand about scratches is that it describes a reaction pattern in the skin, not a specific infection. Researchers classify EPD as a cutaneous reaction pattern rather than a standalone diagnosis, meaning the visible signs (crusting, scabbing, swelling, oozing) can result from bacteria, fungi, mites, immune reactions, or chronic moisture, often in combination.¹ That distinction matters because treating “scratches” with a single antibiotic ointment, for instance, will fail if the underlying driver is a mite infestation or a contact allergy. Many frustrating relapses trace back to addressing only one layer of a multi-layered problem.

What It Looks Like and How It Progresses

Scratches can range from mild flaking that you barely notice while picking out a hoof to painful, swollen masses that make a horse visibly lame. Research on draft horses with chronic pastern dermatitis has broken the progression into roughly four stages: early scaling, thickened hyperkeratotic plaques, raised nodular skin masses, and finally warty (verrucous) growths. Biopsy work shows a gradual increase in epidermal thickening from one stage to the next, suggesting that these are not separate conditions but different points on the same continuum.²

In the earliest stage you might see flaky, slightly reddened skin in the hollow of the pastern. Left untreated, the area starts to weep, and sticky crusts form. The skin underneath those crusts is raw, tender, and often bleeds if the scabs are pulled off. Some horses stomp or resist having their lower legs handled. In advanced cases the skin thickens into hard, warty tissue that cracks and bleeds, and the surrounding area may swell considerably. At this point the horse can become lame enough that an owner mistakes the problem for a structural injury. One case report documented a mare that became acutely lame from severe swelling in a hind leg, initially suspected to be a fracture; diagnostic workup instead revealed chronic pastern dermatitis complicated by a bacterial infection that had triggered inflammation of the blood-vessel walls.³

The Many Causes Behind the Same Skin Reaction

Because scratches is a syndrome, there is rarely one neat explanation for a given case. The causes tend to overlap and reinforce one another, but they fall into a few broad categories.

Bacteria and Other Microbes

For years, the bacterium Dermatophilus congolensis was treated as the primary culprit behind mud fever. Current understanding has shifted: EPD is now linked to a mixed microbial picture shaped by environmental conditions rather than a single organism.⁴ When researchers cultured samples from a dozen cases, they found a grab bag of bacterial species; Dermatophilus showed up on smear in only two of those cases and grew in culture from just one.⁴ Staphylococcal species, various streptococci, and sometimes fungi like dermatophytes or Malassezia can all colonize broken pastern skin. In one documented case, Staphylococcus intermedius drove a serious vasculitis in a horse’s pastern.³ The practical takeaway is that a vet swabbing and culturing the affected area is genuinely useful: it narrows down which organisms are involved and whether an antifungal, antibacterial, or both are needed.

Chorioptic Mange Mites

A surprisingly common contributor that owners often overlook is Chorioptes bovis, the leg mite. These surface-dwelling mites feed on skin debris rather than blood, which means they do not burrow deep enough to trigger the dramatic hair loss you see with other mange types. Instead, they cause itching, stamping, and crusty dermatitis around the pasterns and fetlocks that looks indistinguishable from “plain” scratches. Clinical trials on infested draft horses have scored their pastern lesions using the same mild-to-chronic-proliferative scale used for EPD in general, underscoring how much the two overlap.⁵ Draft breeds with heavy feathering are most susceptible because the long hair traps moisture and provides cover for mites, but any horse can pick them up from shared bedding or turnout areas.

Moisture and Environment

Chronic wetness is the single biggest environmental trigger. Standing in muddy paddocks, repeatedly washing legs without drying them, or turnout on soggy pasture softens the outer skin barrier until bacteria and fungi can invade. Research on young horses found that the interaction between moisture and opportunistic pathogens appeared to be a major triggering factor for EPD.⁶ That same study also found that nonpigmented (white or pink-skinned) pastern areas were affected far more often than pigmented ones, which aligns with what most horse owners already suspect: white socks are scratches magnets.⁶

Immune and Allergic Factors

Some horses develop pastern dermatitis from contact irritants (certain bedding materials, topical products, or plants) or photosensitivity, where unpigmented skin reacts to UV exposure. Vasculitis, an immune-mediated inflammation of blood vessels in the skin, can also produce pastern lesions that closely mimic classic scratches. These immune-related causes are harder to identify without biopsy but are worth considering when standard antimicrobial treatments fail to resolve the problem.

Which Horses Are Most at Risk

Draft breeds and draft crosses top every veterinarian’s mental list. Clydesdales, Shires, Belgians, Friesians, and various European draft breeds have heavy leg feathering that traps moisture, dirt, and mites close to the skin. Some of these breeds also carry a genetic predisposition toward chronic progressive lymphedema (CPL), a condition where the lymphatic system in the lower legs gradually fails, leading to persistent swelling and thickened skin that looks like an extreme version of scratches. Genome-wide research in Friesians has found physical differences between CPL-affected horses and controls, though no single genetic marker has been pinpointed.⁷ CPL cannot be cured, only managed, but controlling its mite and infection components can slow its progression considerably.

Beyond drafts, any horse with white legs, prolonged exposure to wet footing, or a compromised immune system is at higher risk. Horses kept in poorly drained paddocks through winter and spring are the textbook candidates, but scratches also shows up in well-managed barns when legs are washed frequently and not dried properly afterward.

Treatment Approaches

Because so many causes overlap in a typical case, treatment usually involves several steps running in parallel rather than one magic product.

Cleaning and Drying

The foundation of every treatment plan is getting the affected skin clean and keeping it dry. Gently soaking and softening crusts (rather than ripping them off, which tears the healing skin underneath) with a mild antimicrobial wash is the usual first step. Chlorhexidine-based shampoos are widely used in practice. After washing, thorough drying is non-negotiable. Owners who scrub their horse’s pasterns clean but then turn the horse out into a wet field are essentially resetting the clock every day. Treatment literature consistently emphasizes keeping the limbs clean and dry as the baseline requirement alongside any topical or systemic therapy.⁴

Topical Antimicrobials and Barrier Products

Once the skin is clean and dry, topical treatment targets whatever organisms are present. Antimicrobial creams, silver-based wound dressings, and zinc-oxide barrier pastes all see regular use. The choice depends partly on culture results and partly on the stage of the lesion. Early, weepy cases benefit from drying agents; chronic, thickened skin may need emollient-based products to soften crusts and let medication penetrate. Some practitioners use antimicrobial wound-contact products that work by binding bacteria on the skin surface rather than releasing chemical agents into the wound bed.

Treating Mites

If chorioptic mites are involved, you need an antiparasitic alongside everything else, or the problem will keep coming back. A clinical trial in Belgian draft horses showed that moxidectin applied directly to the affected lower legs produced a significant drop in both lesion scores and itching within just seven days, with no signs of itching at all by day 56.⁸ Other trials have compared injectable doramectin with topical fipronil and found that while both eliminated mite-related behavioral signs (stamping, rubbing) by about four weeks, the visible skin lesions were slower to improve, and skin scores did not drop significantly in either group during the study period.⁹ That gap between killing mites and healing the skin they damaged is common. You can clear the infestation relatively quickly, but the dermatitis itself takes weeks of supportive care to resolve. Relapses of chorioptic mange are also frequent, partly because mites survive in the environment and reinfest horses after treatment ends.⁵

Systemic Therapy

Severe cases, especially those with significant swelling, cellulitis, or suspected immune involvement, may require systemic antibiotics chosen based on culture and sensitivity results. Horses with vasculitis-related pastern dermatitis sometimes need anti-inflammatory medications. A veterinarian deciding between topical-only and systemic treatment is typically weighing how deep and widespread the inflammation has become. Mild, superficial cases rarely need oral or injectable drugs; painful, swollen legs with heat and lameness almost always do.

Prevention and Management

Preventing scratches is largely about managing the environment and the horse’s skin barrier. The fundamentals are straightforward even if executing them takes effort:

Drainage: Keep turnout areas as dry as possible. Gravel pads around gates, water troughs, and high-traffic zones help reduce standing mud.
Dry legs: If you wash your horse’s legs, towel-dry them afterward. Leaving legs wet in cold weather is an open invitation.
Feather management: In breeds with heavy feathering, clipping the pasterns makes it far easier to see early problems, dry the skin, and apply treatments. Many draft-breed owners clip through the wet season and let the feathers grow back for shows.
Bedding hygiene: In stalls, damp bedding sitting against the pasterns all night replicates the same moisture problem as a muddy field. Deep, dry bedding matters.
Mite control: In barns with known chorioptic mite issues, treating all horses in the group (not just the symptomatic ones) and decontaminating shared grooming tools and leg wraps reduces reinfestation pressure.

Do Essential Fatty Acid Supplements Help

There is growing interest in whether dietary omega-3 fatty acid supplementation can strengthen the skin barrier enough to reduce scratches. A feeding trial supplementing healthy horses with camelina, flaxseed, or canola oil found that skin omega-3 fatty acid content increased over time while the omega-6 to omega-3 ratio dropped. However, the actual differences in skin fatty acid profiles between the three oil groups were small, and immune and inflammatory markers were comparable across all treatments at the dose tested.¹⁰ In other words, adding an omega-3-rich oil to the diet does change what shows up in the skin, but whether that change is enough to meaningfully protect against EPD is still an open question. The supplements are unlikely to hurt, but they are not a substitute for environmental management and targeted treatment.

A separate trial tested topical essential fatty acid spot-on preparations, applied weekly to the pasterns of young horses. The spot-on groups (one with and one without an added antibacterial compound called phytosphingosine) did not prevent scratches from developing, but affected limbs in both treatment groups had lower lesion severity scores than untreated controls.⁶ The fact that the addition of phytosphingosine made no extra difference suggests the fatty acids themselves were doing the heavy lifting, possibly by reinforcing the skin’s lipid barrier.

When Scratches Becomes Something Bigger

Most cases of scratches are annoying but manageable. The ones that should concern you are those that do not respond to reasonable treatment within a few weeks, those accompanied by severe leg swelling, and those in draft breeds where CPL may be complicating the picture.

Persistent or worsening pastern dermatitis warrants a veterinary visit that goes beyond a visual check. Skin scraping can detect mites. Culture and sensitivity testing can identify bacteria and guide antibiotic selection. Biopsy is the gold standard when immune-mediated disease, vasculitis, or unusual causes like squamous cell carcinoma (which can arise in chronically irritated, unpigmented skin) need to be ruled out. In the case of the quarterhorse mare mentioned earlier, it took biopsy to reveal that what looked like a bad case of scratches was actually a blood-vessel inflammatory process driven by staphylococcal infection.³

In draft breeds, the relationship between scratches and CPL is a frustrating feedback loop. Impaired lymphatic drainage causes fluid buildup and skin changes that invite infection and mite colonization, which in turn worsen the swelling and skin damage. Treating the mites aggressively can slow this cycle. The moxidectin trial in Belgians showed positive effects not just on mange-specific signs but on the broader CPL lesion scores as well, suggesting that controlling parasites is one of the few levers owners have for managing CPL progression.⁸

Why Pigmentation Keeps Coming Up

If you spend any time reading about scratches, you will notice that white legs get mentioned constantly, and the research backs this up. Nonpigmented pastern skin lacks the melanin that helps pigmented skin resist UV damage and may have subtle structural differences in its outer barrier. The epidemiological data showing nonpigmented pasterns are far more susceptible to EPD is strong enough that some researchers describe pigmentation as one of the more reliable predictive factors.⁶ This does not mean horses with dark legs never get scratches; they certainly do. But if you are shopping for a horse that will live on wet ground, or you are deciding which legs to watch most closely during mud season, the white ones deserve extra attention.

Photosensitivity adds another layer for unpigmented legs. Certain plants, liver disease, or drugs can make nonpigmented skin react excessively to sunlight, producing burns and dermatitis on the pasterns that look just like classic scratches. When a horse with white stockings develops pastern inflammation during sunny, dry weather rather than the wet season, photosensitivity should be high on the list of suspects. A vet visit and possibly bloodwork to check liver values can help sort this out from the more common moisture-driven form.