I mean to add, and many people don't know this...............
Are you using plastic bowls for food and water? Many animals can have allergic type reactions to these bowls but they are usually on the face.
Just a thought. If you are using plastic, you may want to switch to ceramic or stainless steel bowls.
Could be any number of things but dermatomyocitis is a possibility. The Vet would have to do a skin scraping for that. Might also be mange or mites, also needs a skin scraping. If it were me, I'd have it checked.
see vet: could be allergies or infection or both