Solving Skin Issues on Horses' Legs

What to do when your horse’s legs are lumpy, bumpy, bald, crusty, hot, itchy, runny, scaly, or swollen

Here it is: The first warm(ish) day since late last fall. With an almost childlike enthusiasm, you bound to the barn for an early spring ride. You hear the birds chirping in trees surrounded by blue sky and feel the sunshine, warm on your face. You give the barn door a push and enter.

Ahh, the smell of hay and horses. Then into the tack room, where you’re greeted with the soothing fragrance of leather.

You pick up your horse’s grooming tote, then head to his stall where he welcomes you with a nicker. But when you look inside, your heart sinks. Something isn’t right with his legs. You stoop to inspect them, then close your eyes, taking a deep breath and wondering what your next step should be.

Skin is your horse’s largest organ. As his body’s covering, it not only envelops his form but serves as the first line of defense against the realm of invaders—bacteria, fungus, and much more—that can wreak havoc on both his comfort and beauty.

“Some skin diseases in horses are asymptomatic and bother the owner more than the horse,” says Jeanine Peters-Kennedy, DVM, Dipl. ACVD, ACVP, associate clinical professor of anatomic pathology and dermatology at Cornell University’s College of Veterinary Medicine, in Ithaca, New York. “But certain diseases, like allergies and infections, can make horses’ skin very itchy and uncomfortable.”

Solving Skin Issues on Horses' Legs

Others can lead to swelling (which can cause the skin to slough and allow harmful organisms to enter the horse’s body) or hyperplastic scar tissue, aka proud flesh, or leave permanent scarring, all of which could interfere with movement, says Valerie Fadok, DVM, PhD, Dipl.

ACVD, senior dermatologist with Zoetis Pet Care, based in Bellaire, Texas. She recommends calling your veterinarian, then starting the hosing or soaking process (whichever your horse will tolerate), at any sign of swelling.

Read on for our sources’ take on 10 conditions (in alphabetical order) that could be affecting your horse, how to treat them, and how to prevent them in the future.

Cannon Keratosis (aka stud crud)

Causes Cannon keratosis is a lesser- known chronic cosmetic condition involv ing overproduction of the keratin that forms the stratum corneum (horny outer layer of the skin). Fadok says veterinarians should consider infections such as dermatophilosis (rain rot, caused by bacteria) and dermatophytosis (ringworm, caused by fungus), which can also appear in this area, when diagnosing.

Signs Crusty lesions of unknown origin down one or more hind legs (formerly thought to be from urine dripping on the horse’s legs—thus, the nickname).

Prevention None known.

Treatment There is no cure for this condition, but Peters-Kennedy says it can be improved with once- or twice-daily application of keratolytic (keratin-inhibiting) agents such as a 50% mixture of propylene glycol and water or once- to twice-weekly shampoos with sulfur or salicylic acid that will break down the crust.

Cellulitis (aka phlegmon)

Causes This inflammation of the sub-cutaneous (directly underlying the skin’s surface layer) tissues frequently results from a Staphylococcus or Streptococcus bacterial infection secondary to an injury, such as a cut, scrape, or chemical irritation/contact dermatitis (skin inflammation), or from vasculitis (inflammation of blood vessels).

Signs Redness, warmth, swelling, tenderness, pain, fever.

Prevention Fadok recommends taking care of wounds as soon as they arise and using only nonirritating topical medications on your horse’s skin.

Treatment Peters-Kennedy says treatment is cause-dependent, with diagnosis made via biopsy: If there’s vasculitis, immunotherapy might be required. Otherwise, says Fadok, base treatment on your veterinarian’s recommendation for an antibiotic and, perhaps, topical therapy. She adds that veterinarians often recommend hydrotherapy (cold hosing), as well.

Contact Dermatitis

Causes Direct contact with a substance (such as hoof paints applied above the coronary band, topical medications such as neomycin or antimicrobials, or grass) or abrasion (from sandy pastures) resulting in irritation can cause these inflammatory skin lesions. They can become secondarily infected with opportunistic organisms such as Dermatophilus congolensis (the bacterium that causes rain rot) or Staphylococcus.

Signs Moderate itching, hair loss, skin redness.

Prevention Find and eliminate the cause, though Fadok says it can be tricky to diagnose. In the case of grass, you’d need to take your horse off the pasture and see if he improves, then put him back on it and see if he flares again.

Treatment Fadok advises washing the area with a gentle antiseptic shampoo (diluted, because it can be caustic when concentrated; learn about its properties under mange below) and applying emollients such as petroleum jelly, balms that contain essential oils, or diaper rash-type creams, all of which provide a barrier against the irritating substance. If secondary bacterial infection occurs, ask your veterinarian about adding an oral antibiotic.

Mange

Causes Horses are susceptible to three types of this mite species; however, Chorioptes is most common on the legs. Chorioptes bovis mites (formerly C. equi) feed on skin cells and secretions. The condition is most common in draft breeds with heavy fetlock feathering.

Signs Variable pruritic (itchy) dermatitis with self-induced hair loss, crusting, and skin redness. Signs are more common in the winter.

Prevention Peters-Kennedy says she doesn’t know of a valid preventive method, although some people administer ivermectin, a dewormer that could potentially kill Chorioptes mites. It isn’t a great treatment, though, because C. bovis is a surface feeder rather than a blood feeder.

Fadok adds that because mange is contagious, inspecting any horses entering your premises can help, as can regular exams and fetlock hygiene for heavily feathered breeds. For severe disease, she says, shaving the fetlocks would be the best way to open the area up to air, but many people have these breeds because they love the feathers, and it can take a long time to grow them back out.

Treatment Peters-Kennedy recommends lime sulfur as a topical dip or wash. It’s a concentrate that must be diluted, then applied to hair and skin (and left to dry) once a week for about four weeks. It smells like rotten eggs and will turn gray horses yellow, so it’s not cosmetically pleasing, she says, but it’s a very effective antiparasitic, antibacterial (fighting the bacterial infections that commonly accompany Chorioptes), and antipruritic treatment.

Dermatophilosis typically manifests as crusted and ulcerated lesions.

Rain Rot (aka Rain Scald, ­Dermatophilosis)

Causes Chronic warmth and dampness that macerates (softens) the skin, leaving it vulnerable to entry by D. congolensis bacteria, especially in horses with nutritional imbalances and/or following microtrauma to the skin such as scrapes and insect bites.

Signs Crusted-over ulcerated spots of skin covered by raised spots of hair that can form on the shoulders, barrel, hindquarters, lower legs, and/or faces of horses that regularly stand in wet grass or mud. Peeling off the crusts results in severe pain.

Prevention Fadok says rain rot is contagious, and many horses are permanently colonized with the bacteria, which live in a dormant form on the skin until activated by a combination of dampness and microtrauma to the skin. Keep your horse stalled until grass dries out later in the day, and control insects with a permethrin wipe or spray product to prevent bites.

Treatment Fadok says antiseptic shampoos containing chlorhexidine usually work. Peters-Kennedy prefers lime sulfur, whose antimicrobial properties usually knock the bacteria down. Our sources agree that if topical treatments fail, ­veterinarian-prescribed systemic oral antibiotics such as penicillin or trimethoprim-potentiated sulfonamides (TPSs, oral antibiotics) are the go-to medications for equine skin infections.

Mustangs

Ringworm

Causes Dermatophyte fungus (one of three mold genera: Trichophyton [Trichophyton equinum], Microsporum, and Epidermophyton) grows on skin, hair, and other body surfaces and usually invades the hair shafts, causing them to weaken and break off, leading to hair loss. It’s contagious and often associated with shared equipment such as boots and grooming tools. Fadok says some fungus species (Microsporum gypseum) might also exist in soil, particularly in the South where sandy pastures are common. Abrasions from the sand can make way for M. gypseum invasion. Young horses, such as foals and yearlings, are more commonly affected, as are horses under stress or with concurrent illness.

Signs Rounded, crusted patches of hair loss (hence the word “ring”). It can sometimes appear as pastern dermatitis but can show up anywhere on the horse’s body. Veterinarians diagnose ringworm by examining a stained sample of the crust under a microscope.

Prevention Avoid sharing grooming tools and other training aids unless you can disinfect them. Peters-Kennedy says the organism can live for 18 months under favorable (warm, moist) conditions.

Treatment Peters-Kennedy says mild infections often resolve on their own, but she recommends treating to prevent the disease from spreading. Fadok favors topical antifungals containing azoles: miconazole or ketoconazole shampoo. Peters-Kennedy opts for a leave-on rinse of lime sulfur, as opposed to a shampoo, because it has more residual activity and does not macerate or break hairs like shampooing can, causing the horse to spread contaminated material.

Sarcoids

Causes Peters-Kennedy says these nonmalignant tumors usually occur when the bovine papillomavirus is present along with skin trauma, and affected horses seem to be fairly young (under 6 years).

Signs Sarcoids can be occult (very subtle, often appearing as a circular patch of hair loss that resembles ringworm), verrucous (warty), nodular and fibroblastic (large and ulcerated, resembling proud flesh, but not necessarily associated with a wound), or malevolent (cancerlike). They most often develop on the head, belly, groin, and legs and can be invasive and recurring.

Prevention Veterinarians believe the virus might be transmitted by fly bites, so be attentive to fly control, says Fadok. Also, tumors usually form where skin trauma has occurred, so try to prevent wounds and abrasions. The tumor seems to be associated with horses that have a particular major histocompatibility complex (immune system) gene.

Treatment Sarcoids are difficult to remove because it’s hard to get clean margins, but they don’t metastasize (spread or migrate to internal organs) so aren’t usually fatal. Fadok recommends leaving occult sarcoids alone. Although they don’t improve, they might not get worse. But, they can progress to the fibroblastic form. There’s no set-in-stone course of treatment, so consult your veterinarian to determine what’s best for your horse. Peters-Kennedy says possibilities include surgically debulking the tumor in addition to chemotherapy, such as cisplatin injections.

Staphylococcal Infections

Causes The bacterium typically causes pus formation, especially in skin and mucous membranes. It’s always secondary to another condition or has an underlying cause, such as allergies or parasites.

Signs Annular (round) areas of alopecia (hair loss) and crusting. With those signs, staphylococcal infection is the veterinarian’s first differential diagnosis (then ringworm, then dermatophilosis).

Prevention Prevent skin trauma, and treat underlying causes such as allergic dermatitis or external parasites, says Peters-Kennedy. And, adds Fadok, practice good hygiene (groom thoroughly using meticulously clean grooming tools), and remember that Staphylococcus species are opportunistic, tending to take advantage of damaged tissue.

Treatment Topical or oral antibiotics. If the signs are localized, says Peters-­Kennedy, apply lime sulfur; if they’re widespread, then use TPS or topical chlorhexidine according to your veterinarian’s advice. Fadok adds that if routine measures don’t work, contact your veterinarian to check for methicillin-resistant Staphylococcus aureus infections that require a culture and sensitivity test for diagnosis and treatment.

Vasculitis

Causes While the reason for this ­inflammation of blood vessel(s) usually isn’t known, it’s commonly due to photosensitization (a severe dermatitis that occurs when certain plant pigments damage nonpigmented skin cells in response to sun exposure). Veterinarians note it more frequently in white-haired skin (so on legs and stockinged areas such as fetlocks and cannons).

Signs Skin reddening, swelling, and crusting with eventual ulceration. Generally symmetric (in both of a pair of limbs).

Prevention Figure out the cause, and eliminate it. If that’s photosensitization, then prevent exposure to direct sunlight by wrapping your horse’s legs and/or turning him out in the early morning and/or late evening rather than during the day.

Treatment If you don’t know the cause, which Peters-Kennedy says is common, treatment usually consists of topical anti-inflammatory medications (glucocorticoids, aka steroids) or, if you’re worried about overusing steroids, a non-steroidal called pentoxifylline. If those aren’t effective, your veterinarian might try administering oral steroids.

Warts (Viral Papillomas)

Causes Equus caballus papillomaviruses (EcPV), nine of which are known in horses (compared to more than 200 human papillomaviruses), cause a hard skin growth that is usually benign but contagious.

Signs EcPV-1 most commonly appears on young horses’ lips and muzzles but can also appear on their lower legs. You might see cauliflowerlike raised, scaly gray masses, sometimes near the hoof, that spontaneously resolve over months as the horse’s immune system develops.

Prevention Prevent spread to other young horses by isolating affected animals, says Peters-Kennedy.

Treatment None needed, because lesions usually resolve on their own in one to three months. However, Fadok says if you have multiple warts and/or lots of foals or yearlings, you could remove the warts using cryotherapy (freezing) or surgical lasers, or your veterinarian might crush the warts, which is thought to release antigenic proteins and, thereby, generate an immune response.

Take-Home Message

Some leg crud is purely cosmetic; other types can be very painful and debilitating for your horse. As you would for any medical issue, consult your veterinarian to determine the type of skin problem plaguing your horse, the best course of treatment, and how to prevent its recurrence or spread to other horses.