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Bacterial & Fungal Skin Infections in Horses: Causes, Symptoms & Treatment

There are several types of skin infections that horses can get from bacterial or fungal sources. 

What causes bacterial and fungal skin infections?

All horses are vulnerable to developing skin infections. Most of these skin issues are exaggerated by warm, humid weather.

Horses were designed to live in colder climates, so they have an undercoat as well as a regular coat. Their undercoat works to trap heat radiating from the body and block water coming from the environment. Unfortunately, those same properties cause the undercoat to trap heat and water vapor coming off the body. This creates a sauna at the skin level, creating the perfect environment for bacteria to thrive.

Body clipping increases your horse’s risk of skin infections by causing tiny amounts of damage to the skin and removing the protective layer of hair making it easier for water to get all the way down to the skin, and poor grooming practices can also lead to an increased risk of skin infection. 

What are the symptoms?

Rain Rot

Dermatophilosis (rain rot or mud fever) is a bacterial skin infection that causes streaks of hair loss that can resemble paint brush strokes, sometimes with matted hair, oozing, and crusting. White head and leg markings are most commonly affected, especially if horses are constantly exposed to wet grazing areas. This can happen in any climate, but it is more common in tropical and subtropical regions and often worsens in the legs with age.


Dermatophytosis (ringworm) is probably the most common fungal skin disease in horses worldwide. The appearance of ringworm can vary dramatically, but in classic situations, it starts as hair loss in a localized area that slowly expands larger and larger. Ringworm generally heals within a few months without treatment; however, it is uncomfortable for the horse and highly contagious to other horses and humans.


Thrush is an infection of the frog that produces a foul-smelling black discharge. There is pain on applying pressure to the area. The hind feet are more often affected than the front feet and, occasionally, infection may result in a general swelling of the distal limb.


Clinical signs vary, but initially owners might notice edema, redness and scaling, rapidly progressing to oozing, hair matting and crusting. Secondary bacterial infection is a common complication and can perpetuate the signs.

How do you treat bacterial and fungal skin infections?

Decrease exposure to wet environments since excessive bathing or lack of shelter from rain can predispose your horse to skin infections. Prevention starts with regular grooming and good nutrition to keep the immune system strong enough to fight off bacteria. Check for telltale bumps and crusts on your horse’s skin and treat immediately if present.


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