Pastern Dermatitis in Horses

Pastern dermatitis is a broad term for inflammation and infection of the skin on the lower limb, especially around the back of the pastern, heel bulbs, and fetlock. You may also hear it called scratches, mud fever, greasy heel, or dew poisoning. In many horses, it starts as mild irritation with matted hair or flaky skin, then progresses to crusts, scabs, oozing, and painful cracks.

This condition is not always caused by one single germ. Instead, it is often a multifactorial skin problem. Moisture, mud, friction, sun sensitivity in unpigmented skin, feathering that traps debris, mites, and overgrowth of bacteria or fungi can all contribute. That is why one horse may improve with basic skin care, while another needs a more detailed workup.

Some horses are more prone to repeat flare-ups. Draft breeds and horses with heavy feathering are at higher risk, and horses with white or lightly pigmented lower legs may be more vulnerable to irritation and photosensitivity-related skin damage. Early treatment matters because chronic inflammation can lead to thickened skin, deeper fissures, and occasional lameness.

Pastern dermatitis usually develops when the skin barrier is damaged and then irritated further by the environment or microbes. Wet footing is a major trigger. Mud, standing water, damp bedding, and repeated washing without careful drying can soften the skin and make it easier for bacteria and fungi to overgrow. Friction from sand, grit, or poorly cleaned boots can add to the damage.

In some horses, secondary infection is only part of the story. Chorioptic mites are an important cause of itchy lower-leg dermatitis, especially in draft breeds with feathering. Dermatophilus bacteria can create crusting lesions, and other bacteria or yeast may complicate an already inflamed area. Photosensitization can also affect horses with white or lightly pigmented pasterns, particularly when sunlight and moisture combine to irritate the skin.

Conformation, coat type, and management matter too. Horses with heavy feathering trap moisture and debris more easily. Recurrent cases may also be linked to allergies, contact irritation, or chronic environmental exposure. Because several problems can look similar, your vet may need to sort out whether the main driver is moisture, mites, infection, sun sensitivity, or a combination.

Your vet usually starts with a hands-on exam and a close look at the pattern of lesions. History is important. They may ask when the problem started, whether it worsens in wet weather, if one or multiple legs are affected, whether the horse has feathering or white lower limbs, and what products or wraps have been used at home.

In straightforward cases, your vet may diagnose pastern dermatitis based on the appearance and location of the lesions. If the condition is severe, painful, recurrent, or not responding as expected, additional testing can help guide treatment. This may include skin scrapings to look for mites, cytology to check for bacteria or yeast, culture when infection is significant or persistent, and sometimes a biopsy if the skin is unusually thickened, ulcerated, or the diagnosis is unclear.

Your vet may also assess for complications such as cellulitis or lameness. That matters because a horse with deep cracks, marked swelling, or pain may need a different treatment plan than a horse with a few superficial scabs. A targeted diagnosis helps avoid over-treating, under-treating, or missing an underlying cause.

Prevention focuses on protecting the skin barrier and reducing moisture. Keep turnout areas, stalls, and gateways as dry as possible, especially during rainy seasons. If your horse comes in with muddy legs, rinse only when needed and dry the area thoroughly afterward. For horses with feathering, regular grooming and thoughtful trimming can improve airflow and make it easier to spot early lesions.

Clean boots, wraps, and grooming tools regularly, and avoid sharing them between horses when skin disease is present. Check the pasterns often, especially in draft breeds, horses with white lower limbs, and any horse living in wet conditions. Catching a few crusts early is much easier than treating deep fissures later.

If your horse has repeated flare-ups, work with your vet on a prevention plan that matches your horse’s risk factors. That may include changes in turnout timing, bedding, feather management, parasite control, or skin-care products. The goal is not perfect legs every day. It is reducing the triggers that let inflammation and infection take hold.