If you find weird, red, scabs, things, on the back of the pastern, it is probably Scratches. Scratches is kind of like the equine equivalent of athlete’s foot. Usually a fungal disease, a secondary bacterial infection commonly occurs as well. What to do?
Keep the footing dry inside the stall and turnout area; use dry bedding and fill in muddy areas around gates.
Dry your horse’s legs before putting him up in a stall.
Avoid early morning turnout when there is heavy dew or frost on the ground.
Do not use wraps or boots that will retain moisture around the infected areas. Do not share boots between horses.
Horses with long leg hair or feathers may benefit from hair removal/clipping so that moisture and contaminants are not trapped against the skin.
Clip the affected area.
Wash with infected area with Ivory Bar Soap everyday and towel dry.
There are many anecdotal applications for treating Scratches. At the end of the day, you are fighting a bacterial and fungal infection. Keep it dry. Keep it clean. And, wash it with good old regular soap.