Sensitive Skin in Horses

Horse owners oftentimes call our Extension office for advice on how to treat skin problems in horses.  They may have one horse out of the entire herd that will have big welts or bumps all over the body.  We usually get these calls in the spring and summer time.  This is because horses are normally more active during the summer, exposed to more sunlight, and insects are vigorous at this time.  There are many issues that can cause skin sensitivity in horses, but the most important thing is to find out the cause before starting treatment.  It is a good idea to pay attention to a horse’s skin and coat as you would any other aspect of the horse’s appearance.  Identifying problems early allows you to catch them before they have progressed to a state where treatment is more difficult.

Some skin problems affect specific breeds, ages, and colors of horses.  Different breeds are predisposed to specific skin problems, either indirectly through breed characteristics like color, or directly through genetics such as HERDA from the Poco Bueno cutting discipline line causing skin stretching and lesion issues. Another example is Cushing’s disease, which causes shedding issues in several pony breeds.  Young horses tend to get warts on their face that will eventually go away with age.  Other issues occur across the board such as Rain rot.  It is a bacterial infection of the skin and appears as crusts with hair loss.  Equine Ringworm is a contagious skin disease, which is caused by a fungus.  Girth itch is a fungal infection of the skin under the saddle and is commonly spread by infected tack.  Saddle sores are a common problem in summer and are usually seen in horses ridden with improperly fitting tack or poor riding technique.  Sometimes a thicker saddle pad is needed or simply sitting up straight instead of leaning forward can correct these problems.

In the Southeast, sunburn is a common problem in non-pigmented skin because of more intense UV light.  High SPF sunscreens, applied and reapplied as needed, can help protect areas that burn.  Some fly sprays provide SPF protection.  Fly masks and sheets may offer additional protection.  Different from simple sunburn is photosensitization, meaning hypersensitivity to sunlight.  Photosensitization appears as severely damaged areas of pink (non-pigmented) skin.  This problem occurs because of the presence of photoactive plant pigments in the skin which, when contacted by UV light, change to a form that damages the skin.  Secondary photosensitization relates to liver dysfunction.  A healthy liver is critical to the breakdown of plant pigments found in all plants.  When the liver does not function properly, these pigments reach high levels in the blood and skin.  The pigments then react to UV light and damage the skin. 

Flies and mosquitoes can be a big problem during summer months.  Even though insects irritate all horses, some are more sensitive than others and develop allergies, with significant breed and individual differences.  For example, Thoroughbred horses tend to be more sensitive to flies than some of the “thicker skinned” breeds.  Culicoides hypersensitivity is an allergic skin disease caused by hypersensitivity to the night biting midge Culicoides.  They are small black flies that are also known as  “no-see-ums.”  They are mostly active at night and can cause the horse to get hives.  Steroids and antihistamines are sometimes used for treatment of severe outbreaks.  To control flies, it is important to remove manure and other waste promptly during fly season.  

Pigeon Fever (also known as Pigeon Breast or Dryland Distemper) is an infection caused by a bacterial organism that is transmitted by stable flies.  The bacteria are carried by the blood stream deeper into the tissues and local lymph nodes, where they cause abscess formation.  The disease is called pigeon fever because horses with abscesses of the chest can have a huge protruding chest, like a pigeon. 

Information adapted by an article written by Douglas O. Thal, DVM.  For more information about skin issues and other disease please see:  http://thalequine.com/articles-client-handouts-and-newsletters-for-horse-owners-by-dr-thal/