08/28/2025
Summertime in the south means horses with dermatitis!! One of the most common forms is “rain rot”. This type of dermatitis is commonly seen along the topline and on the limbs, where the hair tends to stay wet. While many people think that rain rot is caused by fungus, it is actually due to a bacterial infection.
Dermatophilus congolensis is a facultative anaerobic, gram-positive bacteria. The term "anaerobic" means that the bacteria grows best in conditions where there is no air or oxygen. Rain rot occurs when dirt and bacteria are trapped against the skin in the wet, matted hair. A moist pocket is formed around the tuft of hair, keeping out air and allowing the bacteria to grow and thrive. As the infection takes hold, the outer later of skin becomes inflamed.
The most essential part of treatment for rain rot is removing the scabs and tufts of hair, which allows oxygen to reach the bacteria and eliminates the wet, warm, moist, protected environment of the scab. This allows the skin to heal, stopping the bacteria from permeating the skin barrier. It also allows any shampoo and/or medication to reach the bacteria and skin. Scab removal can often be accomplished with a good vigorous grooming. Bathing with mild dish soap, such as white Ivory or Head 'N Shoulders shampoo often helps as well. After the scabs are removed, the inflamed skin is often treated with a topical spray or salve. If your horse has a severe case, he may need sedation for scab removal and/or treatment with a systemic antibiotic as well. Your veterinarian can guide you on the best options for your horse.
Prevention is difficult in this type of weather, but if your horse is especially prone to rain rot, keeping him dry is essential. Good, consistent grooming and clipping can also help prevent this frustrating disease. If you are struggling with dermatitis in your horse, give us a call!!
