Horses are prone to a number of different skin conditions and diseases. Some are minor and resolve on their own, while others can be much more serious.

Skin conditions may affect localized areas on the horse, such as the legs or abdomen, or they can be widespread, affecting multiple areas. Symptoms may include itchiness, swelling, hair loss, skin flaking, and more.

Learning to recognize various equine skin diseases is important to take the appropriate actions needed to resolve the problem or to manage the horse to keep them more comfortable.

In this article, we will discuss how to identify common infections and conditions affecting your horse’s skin, as well as treatment protocols. If your horse shows signs of a skin problem, consult with your veterinarian to obtain an accurate diagnosis.

Equine Skin Diseases

Skin is the largest organ of the horse’s body. Along with the hair coat, hooves, sweat and oil glands, it makes up the integumentary system.

One of the primary functions of the skin is to protect your horse from external factors such as bacteria, chemicals, and extreme temperatures. Skin also acts as an immunologic barrier and is often the first organ to come in contact with environmental allergens.

Skin is made of two layers: the outer, nonvascular epidermis and the inner, vascular and sensitive dermis. The horse’s epidermis comprises 5-7 cell layers, not including the horny layer of haired body skin.

The dermis supports many other structures in the body such as blood and lymph vessels, hair follicles, muscles, nerves, and glands. [1]

Horses’ bodies are covered in hair, adding further protection from outside factors. Diseases and conditions of the skin also commonly affect the hair, which horse owners typically notice first.

Below are some of the most common skin conditions seen in horses and signs you can use to identify these diseases in your horse.

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Sarcoids

Sarcoids are the most common skin tumor found in horses. They can also affect other equids including zebras, donkeys, and mules. Sarcoids are not cancerous, but they can be invasive and are seen as cosmetic defects. [2]

Sarcoids are usually associated with two types of bovine papillomaviruses, BPV1 and BPV2. However, some biopsied sarcoids are not associated with either virus, and the cause is unknown in those cases. [2][3]

Sarcoids can occur in horses of any age, but they are most common in younger horses. They usually appear on the head, limbs, neck, and shoulder but can form anywhere on the horse’s body. [2]

Sarcoids usually aren’t serious, but they can become ulcerated and infected. If they form near the eye, they can also impair the animal’s vision. [2]

Sarcoids can vary quite a bit in their appearance and there are five general types that exist in horses:

  • Occult: Flat patch where hair is absent with a grey, scaly surface. Often circular in shape and commonly confused with ringworm. Usually occur on the face, neck, or between the back legs.
  • Verrucose: Wart-like and scaly but extend deeper into the tissue than the occult sarcoid. Often irregular in shape, and multiple lesions may appear.
  • Nodular: Lumps form under the skin and often appear shiny. These vary in size–some being more than 5 centimeters in diameter. Usually occur around the groin and eyelids.
  • Fibroblastic: Usually a fast-growing, fleshy mass which can begin as a complication of a skin wound. Often become ulcerated and “hang” on a stalk. Can become extremely invasive into the surrounding skin. This is the most common type of sarcoid.
  • Mixed: A variable combination of two or more types of sarcoids, often appearing at different times, forming a “colony”.

Sarcoids can be difficult to treat and may return after treatment. Because of this, they can be a frustrating condition for both veterinarians and horse owners. In some cases, however, sarcoids will resolve on their own. [4]

The most effective treatment for sarcoids is usually complete removal of the lesion and surrounding skin. Other treatments, including topical or injectable products, have been successful, but no treatment is effective in 100% of cases. [4]

Pastern Dermatitis

Pastern dermatitis, also known as scratches, greasy heel, mud fever, mud rash, cracked heels, or dew poisoning, is another common problem that affects the skin on the horse’s lower legs.

This condition is characterized by lesions that form on the back of the pasterns and it can be severe in some cases. Pastern dermatitis can occur in any breed of horse, but is most common in draft breeds or other breeds with heavy feathering on the lower legs. [5][6]

Horses with pastern dermatitis may develop chronic wounds with persistent inflammation. Pastern dermatitis also tends to be a recurring condition. [5]

Treatment for pastern dermatitis will depend on the underlying cause. Clipping and cleansing the area, antibiotics, and topical corticosteroids are the most common treatments, however. [6]

Sweet Itch

Sweet Itch, also known as Queensland itch, summer eczema, summer dermatitis, or insect-bite hypersensitivity, is the most common allergic skin disease in horses.

It is most often caused by the Culicoides insect (often called midges) which inject salivary gland proteins into the horse’s skin when they bite. These proteins cause sensitization and allergies in predisposed horses. [7]

Horses with sweet itch have intense itching and often rub the affected area, resulting in open wounds and secondary infections. The mane, tail, and withers are most often affected. [8]

Most horse breeds are susceptible to sweet itch, but the prevalence varies from country to country. Icelandic horses exported to other areas appear to be most at risk for developing the condition. [8]

Sweet itch is notoriously difficult to treat. Treating this condition involves preventative measures such as protection from Culicoides by stabling the horse from dusk until dawn, and using special blankets, and insect repellents. Glucocorticoid therapy can be used as well. [7]

Rain Rot

Streptothricosis is commonly referred to as rain rot or rain scald. This condition is characterized by oozing, crusty lesions and matted hair. It can occur not only in horses but in other mammals as well. Rain rot is most common in warm, humid areas with rainy seasons. [9]

The good news is that this skin condition often resolves within 14-21 days if the horse is kept out of the elements. However, some horses can develop chronic cases which result in hair loss and thick, crusty skin in affected areas.

Severe rain rot is also associated with lameness, performance loss, secondary infection, spontaneous abortion, and even death. [9]

Treatment of rain rot usually includes the use of medicated shampoo with chlorhexidine and keeping lesions dry until they resolve. Antibiotics may be used in severe cases. Researchers have also found that applying tea tree oil and other essential oils may improve afflicted areas. [9]

Eosinophilic Granulomas

This common skin condition is characterized by non-cancerous lesions most often reported in spring or summer. They appear as raised, non-painful nodules with normal overlying skin usually forming in the saddle region or neck of the horse.

They can range from less than one centimetre to over ten centimetres in diameter. [4]

In rare cases, a horse may have large numbers of eosinophilic granulomas spread across the body. Surgical removal of lesions is the most common treatment. However, glucocorticoids injected into the lesions or given orally may also be effective. [4]

Melanoma

Melanoma is one of the most serious skin conditions affecting horses. It appears as a black lump or multiple lumps usually forming under the horse’s tai