Many causes have been associated with this dermatitis, including: microorganisms, allergies, photosensitivity, nutrition, irritants and soil or bedding conditions. The most common cause is chronically muddy, wet and unsanitary conditions-the kind of conditions you see in small pens.
The most effective treatment I've seen is the use of SMZ, which is basically sulphur tablets made into a paste. This paste should be applied to the cleaned and dried infected area. You can get the tablets from you veterinarian and apply the paste yourself.