Common Skin Conditions in Horses

Are you noticing bumps on your horse’s skin? There are many different problems that can affect the skin of a horse. These issues can range from very simple allergies or dermatitises to parasites or tumors such as sarcoids and melanomas.

When dealing with horse skin conditions, it is important to understand the root cause of the issue to treat it effectively.

What Skin Conditions Can Horses Get?

If you notice anything off about your horse’s skin or coat, it is always best to contact your veterinarian. Many horse skin diseases can appear similar to each other, and your vet can help you properly identify and treat the root problem.

Skin disorders in horses can be broken down into several categories:

Dermatitis

The term dermatitis is generally used for skin problems that cause redness, irritation, and inflammation. Horse skin problems that fall under this category include:

• Scratches/pastern dermatitis/greasy heel: This is the most common condition affecting horses. Damp conditions and skin irritation lead to bacterial overgrowth, which causes redness, flaking, and crusting of the skin, typically on the legs and pasterns.

• Thrush: This is another overgrowth of bacteria and fungi, this time in and around the frog (fleshy center) of the hoof. Thrush leads to a bad odor, changes in the frog, and (in rare cases) lameness.

• Rain rot: Secondary to a damp coat (whether that is from rain or being left damp under a blanket after sweating or being given a bath), bacteria and fungus multiply to cause skin irritation. Rain rot appears as clumps or small patches of raised bumps or scabs containing horse hair. They often fall off leaving bald patches.

• Cellulitis: A very small wound or other opening in the skin (including from pastern dermatitis) can allow bacteria to get into the tissue underneath. Once under the skin, the bacteria spreads and causes extensive swelling and edema (swelling due to too much fluid trapped in the body’s tissues under the skin). If left untreated, this infection can spread to the lymph nodes and a horse can become systemically ill.

• Ringworm: Despite the name, ringworm in horses is caused by a fungus found in soil—not a worm. Ringworm leads to hair loss in very characteristic circles. This disease can be spread to humans through skin-to-skin contact. While treating a horse with ringworm it’s best to wear gloves and practice good hand washing.

• Seborrheic dermatitis: This form of dermatitis is characterized by a greasy hair coat and flaking. It can have a combination of underlying causes, including allergies and bacterial or fungal infections.

Viral

Viral skin problems are caused by a virus, meaning an infected horse can spread disease to others. Some of these diseases include:

• Warts: This papillomavirus causes warts to appear primarily on the noses of young horses whose immune systems are not as strong as adult horses. Warts are caused by contact with other affected young horses and typically disappear on their own over time.

• Aural plaques: Another papillomavirus-induced condition in horses, aural plaques are raised solid bumps that form on the inside of the ear. They are unsightly to look at but otherwise benign.

Parasitic

Parasites live in or on horses, where they grow and multiply. Parasitic infections that may cause skin conditions in horses include:

• Mange: There are various mites that cause mange, which leads to itchiness and hair loss. Some of these mites can be spread to humans.

• Lice: Lice infestations are uncommon in horses but cause noticeable itchiness. Lice are also communicable to people.

Atopic/Allergic

Horses can be born with a specific allergy or develop allergies as the seasons change. Skin problems as a result of allergies may include:

• Hives: Just like people, horses can have allergic reactions to things in the environment including pollens, detergents/chemicals on riding equipment, or even components of their own sweat. Hives are raised swellings or bumps on the skin that can be itchy.

• Sweet itch/insect hypersensitivity: These conditions are exaggerated reactions to insect bites that can result in welts, hair loss, itchiness, and other symptoms.

• Granulomas: These are small nodules that typically form along the horse’s back and are made up of collections of allergy-driven immune cells. They are often seen as a response to a sensitivity to detergents or chemicals in saddle pads or other riding gear.

Tumors

Tumors may appear in horses as cancer or as benign growths as a horse gets older. Some common skin tumors in horses include:

• Sarcoids: These tumors can vary greatly in appearance. Although they are not malignant tumors that will invade other organ systems, they can become very large and locally invasive, especially when aggravated by attempted surgical removal.

• Melanoma: These cancerous tumors are most often found in gray horses. Gray horses are predisposed to melanoma development but the underlying cause of the tumor growth is still unknown at this time. They can form anywhere on the horse but are commonly seen around the rectum and tail head.

• Squamous cell carcinoma (SCC): This cancer is most often found in and around the horse’s eyes and on the penis. It can become malignant if not addressed at an early stage. Certain breeds such as Haflingers and Belgians are predisposed to SCC.

Toxin/Liver Injury

As animals that live outdoors, horses may naturally come into contact with toxins that can cause skin problems such as:

• Photosensitization: This condition results in horses becoming excessively sensitive to sunlight, especially on areas with white hair. They will often lose their hair in these areas and develop severe sunburns. There are two pathways that can cause photosensitization: ingestion of toxins (St. John’s wort and others), and liver injury.

If you notice any of the above symptoms of these conditions, contact you veterinarian right away. The sooner horse skin problems are addressed, the less likely they are to spread and cause your horse more discomfort.