Although you may never think about it, the largest organ in your horse’s body is his skin. More than just a fuzzy coat to groom, your horse’s skin not only is his first line of defense against injury and infection, but skin (also called the epidermis) has many other functions, such as cooling (via production of sweat), acting as a sensory organ, and acting as a storage location for important compounds such as water and fats.
Bacteria and fungi are common pathogens in the environment that can thrive on your horse’s skin. Skin infections most commonly occur during wet weather, or when a horse has been standing in wet, muddy, or dirty conditions for lengthy periods of time without being able to dry out.
Pastern dermatitis is one such condition. Commonly known as greasy heel, cracked heels, mud fever, or scratches, this problem can have many causes, be it bacterial, fungal, or chronic inflammation from irritation. This condition commonly appears as red, inflamed, crusty skin at the back of the pastern. Horses with lots of leg feathering, such as draft horses, can be predisposed to this condition, as this extra hair can trap moisture and dirt against the skin. Treatment usually involves keeping the lower legs dry and clean, usually by using drying antimicrobial agents such as dilute betadine and towel drying. Your veterinarian may sometimes apply topical antibiotics to the affected region.
Dermatophilosis, also known as rain scald or rain rot, is a common fungal skin infection in horses. Seen mostly during rainy, wet conditions, this condition forms characteristic “paintbrush” lesions on the horse’s coat, typically on the back and rump. Mild cases often resolve quickly when the horse is treated with a mild antiseptic shampoo and allowed to sufficiently dry out. In more severe cases where the horse’s skin may become tender and inflamed due to secondary bacterial infection, topical or systemic antibiotics may be required.
As many of these conditions are the result of excessive dirt and moisture on the horse’s skin, keeping your horse as dry and clean as possible is the best prevention.
Dermatophytosis is a similar sounding condition; the prefix “derm” means skin. This is more commonly known as ringworm, and contrary to its name, this is actually a fungal infection that causes characteristic round, hairless, scabby lesions. Ringworm can easily be passed from horse to horse and it is a zoonotic disease, meaning humans can contract it too. Ringworm is not life threatening but there aren’t any currently any reliable medications on the market for treating it. Most of the time, keeping the area dry and clean and letting the infection run its course (which is about a month) is the best way to manage ringworm. Disinfecting tack and grooming supplies helps prevent transmission from horse to horse in case of an outbreak.
Click to download a chart of equine skin conditions.
Horses, like people, can have allergic reactions to things in the environment. Insect bites, such as reactions to the “no-see-ums”, or Culicoides flies, are the most common allergy in horses and can cause hives, hair loss, itchy skin, and thickening of the skin. Proper insect control, such as the use of fly spray, fly sheets, and fans can help fight against biting insects.
There are a few common types of skin cancer that affect horses. Sarcoids are the most common tumor in horses and can be challenging to deal with. Firstly, there are many different types of sarcoids; some look like warts, others look more nodular, and yet others may appear simply as a lump under the skin, or look like an irritated skin sore. Diagnosis of sarcoids can be difficult since their appearance is so varied. Additionally, taking a sample of the affected area (biopsy) will sometimes make the sarcoid worse. While this type of tumor will not spread to your horse’s internal organs, it can be locally aggressive. There are a handful of treatment options for sarcoids, such as surgical removal, different types of radiation therapy, and even immune therapy – all of which should be discussed with your veterinarian.
Other common types of equine skin cancer include squamous cell carcinoma (SCC) and melanoma. SCC is sometimes seen near the eye of a horse, and melanomas are common in gray horses. Both of these types of cancers can be dangerous and require veterinary intervention.
Although cancer in horses is virtually impossible to prevent, you can help aid in quick diagnosis by grooming your horse regularly. This gives you a chance to go over your horse’s body to check for any abnormal lumps, bumps, or itchy spots. Regular grooming will also help keep your horse’s skin healthy by removing excess buildup of dirt and grime, and it also promotes circulation. Plus, it’s a great way to bond with your horse.