Rain Rot / Rain Scald
PREPARED BY: Cheryl Sutor 
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 high temperature and high humidity are present. This condition is not life-threatening, so don't worry. However, while the horse has rain rot, any equipment that may rub and irritate the infected skin (such as saddles and leg wraps) should be eliminated.
What causes rain rot?
The organism dermatophilus congolensis causes rain rot. dermatophilus congolensis is not a fungus. It is an actinomycetes, which behaves like both bacteria and fungi. Most people believe that the organism is present in soil, however, this has not been proven. The organism is carried on the horse, who has it in his skin. A horse who has this organism in his skin may or may not be affected.
What does rain rot look like?
Rain rot can appear as large crust-like scabs, or small 1/4 inch matted tufts of hair. There is usually dozens of tiny scabs that have embedded hair and can be easily scraped off. 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.
In the early stages, you will be able to feel small lumps on the horses' skin or hair by running your hand over your horse's coat.