Rusty has similar skin allergies. The vet also put him on prednisone and it clears up in a few days. Well, he has been off the steroid for about 2 weeks and his rash is starting to come back. We had allergy tests done and nothing has come back. They thought it was something in the yard, but we just moved and still there. We just switched him to Premier Edge Salmon dog food, which the vet thinks it could be a food allergy, so we will see. Any suggestions??