Skin Problems in Horses: The Creeping Crud

Dealing with skin problems, unfortunately, is part of having a horse. Since skin is the largest organ of the body, it's no wonder there's much that can go wrong. Designed to safeguard internal organs from external forces and to help maintain consistent temperature, water, and nutrient levels, the skin is an integral part of a horse's health. The dermis (or the supportive structure for the skin) contains the nerve endings, blood vessels, and epidermally derived structures, hair follicles, and sweat glands. The epidermis is a living structure of cells that constantly renews itself. It produces the outermost layer of dry, dead, hardened cells that form the ultimate barrier between animal and environment. Disruptions in this barrier result from a number of causes. In this article, several veterinarians will help you understand and better care for your horse's skin and the problems it encounters.

Clyde Johnson, VMD, alumnus from the University of Pennsylvania, offers some invaluable insights based on his 40 years of equine practice. "Due to its sensitivity, the skin can be easily disturbed," he states. "In fact, many things can upset its fragile balance--from dirty bedding to sunburn--resulting in a variety of conditions that may be particularly frustrating to diagnose, and until the situation is resolved, difficult to treat."

Fairfield Bain, DVM, MS, Dipl. ACVIM, ACVECC, ACVP, in an article published in Equine Disease Quarterly (April 2001), says it is important to identify the types of lesions observed. The most common include:

  • Papule--a solid skin elevation;
  • Pustule--a skin elevation with an inflamed base that contains pus;
  • Vesicle--a membranous and usually fluid-filled pouch;
  • Bulla--an elevation containing watery fluid;
  • Wheal--a flat, burning, or itching lesion;
  • Macule--a patch of discolored skin; and
  • Nodule--an abnormal, knobby protrusion.

He adds, "The pattern or distribution of skin lesions is helpful in determining a cause. Certain hypersensitivity reactions to insects might involve the mane and tail region, whereas nodules resulting from allergic collagenolytic granulomas (firm bumps or nodules under the skin) are most commonly found on the chest wall just below the elbow."

While volumes have been researched and written on the subject of skin, below is a partial list of skin ailments you're most liable to come across during your tenure as a horse owner. If you're able to catch and define them early enough, it should make treatment easier. Remember, get your veterinarian involved early as several diseases exhibit similar signs.

Ringworm (Dermatophytosis)

Contrary to its common name, ringworm is not a worm but a fungal infection. It assumes the form of round, crusty patches, which when removed leave reddened, scaly skin and hair that comes out in clumps. It usually appears first around areas where tack comes into contact with the skin, although the disease can be found anywhere on the body. Highly contagious, ringworm can be transmitted directly from horse to horse, or through inter-species contamination. Dogs, cats, cattle, and even people are often the hosts. It also easily adheres to inanimate objects like tack, blankets, or grooming equipment. And with the spores remaining dormant in the environment for up to a year, everything from your stall and barn to the soil in your paddock can become infected.

Like all fungi, ringworm is happiest in dark, warm, moist conditions; therefore, outbreaks generally occur in the fall and winter months when there is less sunshine and more moisture. "But it is the horse that has become debilitated from an illness, is undernourished, is in stressful surroundings, is on immune-suppressing medications, or is in an overcrowded situation that is especially vulnerable," notes Johnson.

If you suspect that your horse has ringworm, isolate him as best as you can and call your veterinarian to make sure you have the appropriate medications to treat it.

Before using a topical medication, start by clipping about a two-inch portion of hair around each outbreak so that any medicated shampoo and cream will be sure to penetrate that portion of skin most likely to become affected before the fungus is contained. Proper disposal of potentially infected, clipped hair is essential to prevent further contamination of the premises.

Wash your horse with an anti-fungal shampoo--sold at tack shops or by your veterinarian--that is developed specifically to treat ringworm. There are also a variety of topical ointments (also available in tack shops or through your veterinarian) that can be applied to the infected spots. Be sure to wear latex gloves or at the very least wash your hands with an antifungal soap after each treatment.

Clean your tack and equipment using a disinfectant soap in combination with a leather conditioner to keep it soft, and then put it out in the sunshine, a sure remedy. Also, disinfect your blankets, saddle pads, and grooming tools.

Chlorine bleach is an effective neutralizer, but it is extremely abrasive to healthy skin tissue, so be sure to rinse everything thoroughly. You'll also need to sanitize your wash stall, box or standing stall, cross-ties, fences, posts, and wooden gates as anything that has come into contact with the fungus is a potential source of infection.

While in most instances ringworm is self-limiting and will disappear on its own within six weeks to three months, acute infections might require prolonged treatment or reassessment with skin culture, cytology, or biopsy to make sure there is no other underlying problem, according to Bain. Whatever the severity of the case, know that ringworm is a distressing ailment and should be treated to control its spread.

Also, keep in mind that tack should not be placed on affected skin or further skin irritation can occur, and skin can take a long time to heal--imagine yourself wearing football pads when you have a sunburn. This would be true of any skin disease.

Rain Rot/Rain Scald (Dermatophilosis)

Whether you call it dermatophilosis, rain rot, or rain scald, it's a bacterial infection that lives in soil and can inhabit the skin without adverse effect until there is either trauma or repeated exposure to moisture (like ringworm). Horses kept outside where they are fending off insect bites or are left to stand unprotected in the rain are the prime targets. Johnson points out, "Horses that are most at risk are on some level compromised, whether they are undernourished or immune suppressed."

Like ringworm, rain rot is more apt to appear in the fall and winter months and it is believed to be contagious. Infected horses typically develop a series of small bumps that progress into circular scabs with matted tufts of hair, which are quite painful when removed. Lesions are commonly found along the back, rump, neck, and legs.

Horses with rain rot should be kept dry and away from biting insects. Begin a seven- to 10-day cleansing program with a medicated shampoo. The bacteria live under the scabs, which should be detached during the bath when they are soft to spare your horse further discomfort. Proper disposal of infected scabs is important to reduce environmental contamination. Penicillin injections administered by your veterinarian can expedite the healing process, especially if rain rot is detected early.

Rain rot is also thought to be transmitted through shared tack, blankets, and grooming equipment, so anything that has come into contact with the affected horse needs to be disinfected.

A self-limiting condition, rain rot can resolve itself spontaneously once the immune system gets going or when the weather becomes drier; however, the disease can become quite acute before it improves. To prevent further occurrences, avoid having your horse outside during inclement weather without shelter, protect him against fly bites, keep him from being malnourished or immunocompromised, and maintain good grooming habits.

Scratches (Dermatitis)

Dermatitis, also known as mud fever, greasy heel, dew poisoning, or scratches, affects the backs of the pasterns and the bulbs of the heels and is most commonly found in horses exposed to moisture for long periods of time, whether from standing in a muddy field or a wet stall. Constant moisture can become an irritant as it penetrates delicate skin, causing inflammation, redness, and ulcerations. When coupled with dirty surroundings, it can be an ideal situation for infection.

Speed is of the essence when tending to scratches; if left untreated the raw skin will often crack and bleed, inviting a deeper level of infection. It is for this reason that scratches must be treated, since it is not a disease unto itself but stems from a variety of microorganisms including bacteria, fungus, parasites, and allergies. Consult with your veterinarian, who might want to do some laboratory work in order to make the correct diagnosis and treatment recommendation. Without this information to guide treatment, any action could possibly delay or even create complications to the healing process. If the leg or legs should become hot and swollen, it is a sign that the infection has become more serious, in which case your veterinarian might need to prescribe specific medication.

Regardless of the cause, there are several steps that should be taken when dealing with scratches. Start by clipping the long hair from the affected skin in order to keep it clean and dry. Next, wash the area thoroughly but gently, making sure to remove dirt but being careful not to aggravate the skin. Follow by lightly towel-drying the area. Limit your washing sessions to only once a day as additional moisture could further inflame already tender tissue. Also, try to keep your horse out of muddy or wet places and make sure that his bedding is clean and dry. In the future, avoid hosing your horse's fetlocks and pasterns unless you have a specific reason and always make sure to completely dry the area afterwards. You should thoroughly clean any hobbles, boots, or wraps before you use them again.

Hives (Urticaria)

According to Bain, hives is probably the most common immunological equine skin disorder. A systemic reaction to a number of triggers, hives is seen as localized, soft, pitting swellings most commonly found on the neck and chest, although they can appear anywhere on the body. The resulting lesions might emit a clear fluid when pierced. To identify the source is key to the elimination of the problem; however, the task might be challenging as anything from the ingredients in feed or feed supplements to insect bites to pollen, molds, or compounds found in dewormers or antibiotics are all suspect. Contact allergens can even be found in bedding; heat, light, or exercise also could be contributing factors.

Johnson says that horses which have developed hives are best cured by removing the irritant once it is recognized. In order to do this, you or your veterinarian might have to conduct a series of tests, either by exposure to the possible cause or through intradermal testing.

"Hives are symptoms and should be treated immediately even if the cause is unknown in order to prevent further skin deterioration," he adds. If the problem is not immediately resolved, a prescription for antihistamines or steroids might be needed to help speed recovery.

Insect Allergy

Some horses are known to be hypersensitive to insect bites. Insect allergies are identified by intense itching as a reaction to the saliva from Culicoides gnats (no-see-ums) and/or horn, horse, or black flies. The bites also result in crusting, thickened skin, and hair loss as a result of rubbing the affected areas, i.e. ears, face, mane, tail, and groin.

While you might need to call your veterinarian for a prescription to inhibit the allergic reaction and for any secondary infection that can follow, you also can apply an over-the-counter topical product to relieve the itching. Johnson cautions to make sure it is made specifically for horses as human products are often too harsh and can cause burns.

Protect your horse from attack with a fly mask and insect repellents when pastured, and by installing a fan in the stall and mesh wire screens on the windows, if feasible (to make it harder for insects to land on your horse). Also, keep stable and paddock areas free from manure and standing water, as these are prime breeding grounds for pests.

Sunburn and Photosensitivity

"Sunburn can be caused by a direct trauma to the skin, a symptom of underlying disease, or an effect of the presence of certain medications in the dermis," notes Marc McCall, DVM, in a July 1998 article published in The Horse titled "Skin Problems." Typically occurring on the muzzle, around the eyes, and on pink-skinned portions of the face or body, sunburned skin can blister, ooze, and ultimately peel, taking about a week to heal. By limiting exposure to the sun and by applying sunblock creams (you and your horse usually can use the same ones), you can help prevent sunburn from recurring.

While photosensitivity is related to sunburn in that the condition is linked to sun exposure, photosensitivity produces lesions whose characteristics are more severe than those associated with sunburn. Typically found in horses which have areas of depigmented skin and a predisposition to the ailment, redness and inflammation are the precursors to painful open sores that become crusty scabs. When horses which are systemically photosensitive ingest forages that are otherwise harmless but have a photodynamic, or light-sensitive, compound, such as St. John's Wort, red clover, and perennial rye grass, they likely will develop a reaction that causes photosensitivity and makes them more prone to sunburn.

If it's impossible to eliminate the offending plants from your pasture, it would be wise to stable your horse during the daytime and turn him out in the cool of the evening. In addition, your veterinarian might prescribe anti-inflammatory drugs or antibiotics to control swelling and any secondary infections that could develop. There are also topical remedies that can offer comfort and speed healing.

Proud Flesh

Excess granulation tissue, or proud flesh, is the unsightly result of poor wound healing. It's a proliferation of skin tissue that develops in the underlying dermis, resulting in an irregular pink or reddish outgrowth. Proud flesh delays the healing process by becoming an involuntary obstacle to the regeneration of healthy cells, and often needs to be removed surgically or with medication.

Size and location of a wound are significant factors to its formation. A wide gaping lesion that has not been sutured is more likely to develop proud flesh. Lacerations on the lower legs and near joints tend to be the main areas affected.

"In addition, wounds that are not able to be covered by a bandage or held together by sutures are extremely sensitive and susceptible to inflammation, causing proud flesh to develop especially if dirt, bacteria, abrasive soaps, or antiseptics come into contact with them, as well as any disturbance that slows down the healing process such as biting, scratching, rubbing, or excessive motion," emphasizes Johnson.

He says it is imperative that owners begin wound treatment immediately by cleaning the area with warm water and calling a veterinarian to determine whether sutures are needed. Keep the wound as sterile as possible at all times, but stay away from hydrogen peroxide or iodine-based antiseptics, as they are abrasive and actually can lead to proud flesh.


Horses with sensitive skin, such as Thoroughbreds and Arabians, are more prone to this complaint than other breeds; however, seborrhea (skin discharge) can develop in any horse as a secondary condition to skin infection or allergy, or it could be a signal of poor overall health. Seborrhea takes two forms, either dry or oily. Dry seborrhea exhibits dry, flaky scales that look similar to dandruff, and is found in the mane or tail. Thick, viscous crusts usually affecting the elbows or hocks are signs of oily seborrhea.

Wash the area with a sulfur-based shampoo once or twice a week to manage dry seborrhea, although recurrences are common. For oily seborrhea, depending on the severity of the case, wash the area at least twice a week using a drying shampoo (that contains tar or benzoyl peroxide, for instance), followed by a protective ointment to soften the crusts.

Adding corn oil or fatty-acid supplements to the feed will help to improve dry skin. Also, maintain a regular grooming schedule to remove dirt and sweat. A soft curry comb can stimulate the skin to produce naturally occurring oils, which also might help control future outbreaks.


"Skin tumors are some of the most frequent cancers from which horses suffer," states McCall. He goes on to describe the three examples listed below. In all cases, your veterinarian should be contacted to make an inspection and even take a biopsy if there are questions. (See "The Other Cancers" on page 85.)

Squamous cell carcinomas--Typically appearing around the eye or sheath in light-skinned horses, squamous cell carcinomas are lesions of the skin characterized by crusty edges that do not heal. McCall asserts that this tumor usually is very malignant and spreads to surrounding tissues quickly. He advises surgical removal and local chemotherapy as the best chance for cure.

Sarcoids--Thought to be benign viral tumors, sarcoids can develop anywhere on the body, but are usually found around the eyes, legs, and lower abdomen. Most are hair-covered, slow-growing, and present little trouble for several years; however, sarcoids also can be quite aggressive and depending on their size, number, and location, diagnosis and treatment might include radiation therapy, freezing, and intralesional injections of chemotherapeutic drugs. McCall points out that recurrence is quite common.

Melanoma--According to McCall, equine melanoma is generally a benign tumor that forms gray to black hairless nodules, usually underneath the tail, around the anus, external genitalia, eye, or muzzle. Predominantly found in Arabians, Percherons, Lipizzans, or aging gray horses of any breed, there is no known prevention, but growth is slow and often doesn't require treatment. Frequently appearing only as a cosmetic blemish as opposed to the human form of melanoma, life expectancy for the horse is good as this tumor rarely metastasizes internally, although it can ulcerate and become infected.

Genetic Disorders

Congenital skin defects are common to many breeds; some are mostly breed-specific, as with the three following examples.

Epitheliogenesis imperfecta (EI)--Bain states that while EI is seen in several breeds, the American Saddlebred is particularly known for this fatal disease, which is characterized by large, blood-red colored regions of incomplete skin formation that expose the underlying dermis. A genetic mutation that mostly affects the knee and hock areas, tongue, and mouth (and in some cases the hoof wall), foals usually die within a few hours to several weeks of birth. EI is caused by a single autosomal (not gender-related) recessive gene; therefore, if only one parent is a carrier, it will not be expressed in the foal, but the foal might be a carrier.

Hereditary equine regional dermal asthenia (HERDA)--This condition, also known as hyperelestosis cutis (HC), affects the American Quarter Horse in particular. Characterized by skin lesions that typically form under the saddle area, HERDA is recognized by hyper-extensible skin that is easily torn or separated from the underlying dermis. Horses with this condition are not normally diagnosed until the affected area is traumatized, usually when they are two years old and in training. At present, there is no known treatment for HERDA, but it is likely inherited through a recessive gene, since many of the parents of affected horses do not exhibit signs. Stephen White, DVM, Dipl. ACVO, of the University of California, Davis, states that although there is currently no DNA test available for the detection of HERDA and probably won't be for another two to three years, in the future it is hoped that carriers can be identified prior to breeding to reduce the rate of HERDA instances (For more information, see

Chronic progressive lymphedema--This disease is exclusive to certain breeds of draft horses--particularly Shires, Clydesdales, and Belgians--and is characterized by progressive swelling and pronounced thickening of the skin, with encrusted lesions that appear on the lower legs. The problem is often visible only after the long hair around affected areas is clipped. Secondary infections are easily contracted, which might be parasitic (such as chorioptic mange), fungal, or bacterial. Stemming from the lymph system, chronic progressive lymphedema is evident at an early age and progresses throughout the horse's life, causing disfigurement and disability and often leading to premature death.

Take-Home Message

With prompt attention and care, most skin problems can be resolved successfully. However, as with any problem relating to your horse's health, if there is a question, it's wise to consult your veterinarian who can identify the condition and prescribe the most suitable treatment.



Sloet, M. The Practitioners Guide to Equine Dermatology. Leeuwarden, The Netherlands: Uitgeverij Libre BV, 2001.

A systemic reaction; localized, soft, pitting swellings most commonly found on the neck and chest, although they can appear anywhere.
Photosensitivity produces lesions whose characteristics are more severe than those associated with sunburn. Redness and inflammation are the precursors to painful open sores that become crusty scabs.
Rain rot
A bacterial infection; many small bumps progress into circular scabs with matted tufts of hair that are quite painful when removed.

Inflammation, redness, and ulcerations from constant moisture, especially when coupled with dirty surroundings.



Skin discharge, either dry and flaky or oily.



About the Author

Toby Raymond



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