My little dog had the same thing happen last fall. The vet said it might be a thyroid condition. I did not believe it and had him treated for mites....the same kind that gets in the ears of floppy, hairy dogs ears. My dogs skin is very thin and he can get cut very easily. I figured it was the same kind of skin in most dogs ears. We treated him with flea and tick medicine like Frontline but it also killed mites. I think it was called Atvantage??? No more itching and his fur grew back in about a month. Hope you figure it out, it's very frustrating. Oatmeal baths seemed to help to soothe him.