Listing of Horse Skin Disorders

Genetic Abnormalities

• Different breeds of horses are susceptible to different types of skin problems. Hereditary Equine Regional Dermal Asthenia (HERDA) is a genetic abnormality that affects specific lines of Quarter horses. Characteristics of HERDA are abnormally stretchy and easily torn skin. Thoroughbred horses tend to have thinner skin that is extremely sensitive to irritation from bug bites. Many pony breeds suffer from Equine's Cushing's Disease, characterized by long, shedding coats. Horses that are very light-skinned or pink-skinned are highly prone to skin cancers, especially carcinomas. Gray horses have a higher rate of melanoma tumors, especially around the anus, ear, lips, sheath and jaw bone area. These tumors are usually benign in nature, but they can become cancerous or cause skin infections to occur when the horse rubs the hard bumps against a surface repeatedly or bites at them.

Age-related Skin Disorders

• Facial warts are quite common in young horses. They usually go away when the horse matures. Older horses are more prone toward cancerous lesions, which may or may not spread to other parts of the body or the lymph system.

Fungi, Bacteria and Viruses

• Dermatitis of the heel and areas of the lower limbs is usually caused by a fungus or bacteria and may be treated with anti-fungal or antibiotic agents. Dermatophilosis affects horses that have cuts or abrasions on their skin along the back and top line. It is caused by bacteria and may cause a loss of hair around the infected region, as well as a sour odor and wound festering. Another common skin disorder causes aural plaques--a viral condition characterized by small bumps inside of the ear.

Parasites and Allergies

• If your horse is constantly rubbing or biting at his skin, he may have skin allergies. Many horses are allergic to insect bites, most particularly gnat-bites. The condition of irritation caused by constant itching and rubbing of gnat bites is known as "Queensland Itch." Very often the bite will become infected from the constant rubbing, and the hair around the bite area will fall out. A secondary bacterial infection may occur as a result of the horse's rubbing the wound, or the horse may develop a parasitic infection related to the bite, as tiny worms are transmitted through the bite into the area underneath the skin. If you notice that the bite area has become moist and crusty, with much of the hair around it missing, your horse may have a parasite infestation that should be treated with an antiparasitic dewormer right away.
  Inhaled allergens or food allergies can cause red wheel-shaped hives all over the body, as well as swollen eyes or a swollen face. Call your veterinarian right away if you notice these types of symptoms in your horse, as he may be suffering from an acute allergic reaction requiring medical attention.
  Constant rubbing against a surface such as a saddle or bridle may cause irritant contact dermatitis in your horse. Treat the areas with a salve prescribed by your veterinarian, and try to let it heal before letting it come into contact with the irritant again. Pemphigus Foliaceus is caused by a horse's own immune response to his skin. The condition produces blisters, scaly skin and scabs, which can become ulcerated and encrusted if left untreated.
  Horses can contract mange from mites. The condition causes red bumps which heal into scabs, as the hair around the area falls out in clumps. Chiggers are caused by mite larvae and create itchy, broken skin around the head, neck, chest and legs of a horse. Pinworms cause a ratty look to the hair and tail of a horse. They are usually found in younger horses.

Noncancerous Bumps

• There are many types of noncancerous bumps that may afflict your horse. Aside from plain old warts, your horse may have a sarcoid--a cauliflower-like growth that affects horses of all ages. Painful or tender knots can be caused by a reaction to shots and may disappear after a few days or weeks. Cattle grubs can cause holes in the skin and are usually found burrowed into your horse's withers, neck or back.