Common Equine Skin Conditions

Whether you’re spending the winter in the snowy north or sunny south, the weather may pose a few challenges for keeping your horse’s skin healthy. Wet winter conditions paired with heavy blanketing may provide the perfect environment for skin issues to fester. Wintering in the south leaves your horse’s skin susceptible to skin conditions brought upon by the sun and insects. Keep your horse protected this winter! Read about some of the most common equine skin conditions below:

Rain Rot

  • What is it?

    A crusting dermatitis where tufts of hair become raised and shed, usually leaving the patches. Often occurs along the back and croup and may occur on the legs.

  • What causes it?

    A bacterium called Dermatophilus congolensis causes rain rot. It is found in the soil and on horses that are carriers and is spread by flies, shared coolers, tack. The spores from the organism are released when wet, but are unable to invade the skin unless it is damaged.

  • How is it treated?

    Keep the affected area dry and remove the crusts. Clean and try to reduce use of shared equipment. Topical medications containing iodophors, lime sulfur, or chlorhexidine are useful.

Scratches (Pastern Dermatitis)

  • What is it?

    Scratches are a cutaneous (skin) reaction pattern rather that a single disease. Scratches often starts with reddening, swelling, and scaling of the skin on the back of the pasterns. This can progress to crusting, itching, discharge, and hair loss.

  • What causes it?

    There are many potential causes of scratches – this includes bacterial, fungal, parasitic, allergic, traumatic, and immune-mediated causes or a combination of these.

  • How is it treated?

    Generally, therapy is symptomatic, since the causes can be multiple. Firstly, remove the horse from wet and/or conditions. The pastern should be then clipped and gently cleaned. Shampoos should contain antimicrobial agents such as chlorhexidine or benzoyl peroxide. Emollient creams with antimicrobial agents and glucocorticoids may be of benefit if particularly dry or thickened. Lastly, for particularly bad scratches, systemic antibiotics or glucocorticoids may be needed.

 

Ringworm

  • What is it?

    Circular to oval hairless patches that may also have scales or crusts. Commonly occurs on head, neck, girth area, or thorax.

  • What causes it?

    Ringworm is fungal in origin and is usually caused Trichophyton or Microsporum dermatophytes.

  • How is it treated?

    Ringworm can be topically treated with antifungal shampoos or creams containing lime sulfur, enilconazole, or miconazole/chlorhexidine. Additionally, any tack, grooming equipment, or blankets used on the affected horse should be disinfected. Separate equipment should be kept for the affected horse.

 

Sarcoids

  • What is it?

    Sarcoids are the most common equine neoplasm and most commonly occur on the ears, lips, around the eyes, the prepuce, neck, legs, and belly. Sarcoids may appear as flat hairless lesions or raised, irregular tumors.

  • What causes it?

    Bovine papilloma viruses are associated with the development of sarcoids. Sarcoids often occur in area previously subjected to trauma or an injury.

  • How is it treated?

    Sarcoids are usually aggressive locally and don’t regress on their own. Multiple treatment options are available, depending on the size of the tumor. Small tumors may respond to treatment with topical agents such as imiquimod or Xxtera. Larger tumors often need to be surgically excised and followed with treatment with cisplatin, cryotherapy, or laser therapy.

 

Melanomas

  • What is it?

    Melanomas are a common skin tumor of horses, most common in gray horses. The tumors are usually firm and nodular and often occur on the underside of the tail and around the anus, lips, eye and base of the ear.

  • What causes it?

    The cause of melanomas is unknown.

  • How is it treated?

    Cimetidine (an antihistamine with immune system modulation effect) has been reported to help slow or stop the progression of the disease, however results have been variable. If the melanoma is blocking the anus, prepuce, or vulva, surgical excision may be necessary, however this is rarely curative. An intradermal melanoma vaccine is currently being tested in horses.

 

Aural plaques (ear papillomas)

  • What is it?

    Aural plaques are small, white, slightly raised lesions present on the inside of the ears.

  • What causes it?

    Aural plaques are a papillomavirus-induced neoplasm. It is thought that the virus is often transmitted by biting flies, but it can also be transmitted by direct contact or other inanimate objects. For infection to occur, the skin must be damaged, such as from trauma or insect bites.

  • How is it treated?

    Aural plaques rarely spontaneous resolve. Until recently there was not an effective treatment, but a study has just shown that the topical medication imiquimod can cause lesion resolution.

 

Insect-bite hypersensitivity

  • What is it?

    Insect-bite hypersensitivity is the most common allergic skin disease of the horse. The horse becomes very itchy, and as a result usually loses hair in affected areas and may develop excoriations as well. It often occurs along the mane, tail, croup, and girth area.

  • What causes it?

    Usually cause by a hypersensitivity reaction to the saliva of Culicoides species (gnats), although other insects may cause as well.

  • How is it treated?

    Insect control is the most important measure to keep the horse from continually being affected. This includes avoidance of turnout at dusk and dawn, the usual feeding times of Culicoides species. Systemic steroids and anti-itch shampoos are effective at delivering immediate relief to the horse.

 

Hives

  • What is it?

    Hives are edematous nodules or papules in the skin that can occur anywhere on the body.

  • What causes it?

    Hives can be caused by an allergic reaction to something in the environment, the horse’s diet, or medications. Hives can also be caused by physical factors like heat, cold, pressure, or stress or exercise. However, many times that cause of hives is idiopathic, meaning that the cause is unknown.

  • How is it treated?

    In the acute phase, hives are usually treated with systemic steroids. Hydroxyzine (an antihistamine) can be used to treat recurrent or persistent hives. For persistent or recurrent hives, an IDAT (intradermal allergy test) can be performed and an allergy vaccination can be formulated for the horse based on its responses.

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