Rainrot: Take Control

With a few simple steps at the first signs of trouble you can keep this generally minor skin infection from growing out of control.

Often, the first signs of rainrot arise just hours after a horse is brought in from the rain: Tufts of hair begin to stand upright in patches over his back, sometimes following the contours of the “drip line” where water runs off his body. Or the tufts might appear on the legs, where he has been wading in deep, wet grass.

The areas with raised hair feel warm to the touch, and the horse may flinch from contact. By the next day painful, tight scabs will have formed over pockets of yellow-green pus. Rainrot is an infection caused by Dermatophilus congolensis, which usually resides on the skin in a dormant state without causing trouble. However, persistent moisture can activate the bacteria, leading to infection. Advanced age, illness, stress, the administration of corticosteroids or other factors that can compromise immune function increase a horse’s susceptibility to rainrot.

Although it’s not the most serious skin infection a horse can contract, rainrot can cause discomfort and hair loss, so it’s good to get a developing case under control as quickly as possible.

Here’s what to do

• Cleanse the coat with an antimicrobial shampoo. A number of products are labeled for use against rainrot, with ingredients including povidone iodine, chlorhexidine, benzoyl peroxide or other antimicrobial agents. Many are available over the counter and can be very effective in mild cases when used as directed. You may need to repeat the treatment over several days.

• Dry out the coat. Bring the horse into a dry environment and rinse off any dirt or mud that may be holding moisture against his skin. Then let his coat dry thoroughly. If the weather permits and it’s not too painful for the horse, clipping longer hair may encourage air to circulate against his skin.

• Apply a topical antimicrobial product. A number of rinses, washes