Now that you figured it out, try to avoid certain oils. Maybe go with fish oil instead of wheat germ oil. Whoever you got your dog from, you should ask him if he had the same problem. I have a couple of dogs that had a history of mange from that particular line. After some research, i found out that other owners of the same line had the same problem. If they are fed with optimum food(avoid kibbles)and clean housing, you wouldn't even know they were born with that problem. I don't know if this help but that's my version of how I took care of my dog's problem.