So what is rain rot?
Rain rot is one of the most common skin infections seen in horses. It is also referred to as “rain scald” or “streptothricosis”. The organism that causes rain rot appears and multiplies in warm, damp conditions where prolonged wetness, high humidity, high temperature, or attacks by biting insects are present.
This condition is not life-threatening, so don’t worry. Make sure you avoid equipment, such as saddles, or leg wraps, that will irritate skin infected by rain rot.
What does rain rot look like?
Rain rot can appear as large crust-like scabs, or small 1/4 inch matted tufts of hair. Underneath the scabs, the skin is usually (but not always) pink with puss when the scabs are first removed, then it becomes gray and dry as it heals. It is usually hard to differentiate rain rot from other similar skin conditions, so if you are unsure, call your veterinarian.
So what causes rain rot?
“Rain rot or rain scald (also known as dermatophilosis) is caused by bacterial infection, and it often is mistaken for aRain Rot in Horses fungal disease,” says Ann Swinker, PhD, an extension horse specialist at Penn State. “The bacteria live in the outer layer of skin and cause from pinpoint to large, crusty scabs.”
Rain rot occurs when the infective zoospores (created by D. congolensis bacteria to propagate themselves) reach a compromised skin site. Swinker says, “The zoospores germinate and produce hyphae (threadlike tentacles), which penetrate into the living epidermis and spread in all directions, resulting in an acute inflammatory skin condition.”
How to treat rain rot?
Remove the environmental factors that cause rain rot and your horses will heal on their own. Make sure your horse has access to shelter, like a lean-to, during rainy conditions.
A light, breathable sheet may help to protect your horse from rain. Avoid heavier blankets that trap moisture against his skin. Clean and wash all of his tack and equipment thoroughly and take a break from riding if he develops lesions in the saddle area (the saddle will trap sweat against his skin and may cause discomfort while the lesions are active).
When you bathe him, scrape excess water off his body and keep him inside until his coat dries thoroughly. During the buggy season, apply insect repellent regularly.Rain Rot in Horses
These measures will solve the vast majority of rain-rot cases. If your horse’s symptoms persist, ask your veterinarian to recommend a shampoo containing a keratolytic agent, such as benzoyl peroxide. Such products strip away dead layers of skin, along with crusty scabs and bacteria, and help to treat secondary conditions.
I would not recommend treating a topical disease like rain rot with systemic antibiotics. This would disrupt the natural micro-ecology of your horse’s gastrointestinal tract. Treating with systemic antibiotics will also contribute to the broader problem of antibacterial resistance created by the overuse of antibiotics.