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.