If that's not the problem (Mange) then other possibilities are staphlococci infection (treat with a/b's) or diet (change both protein and starch source) or SFA (see recent discussion yesterday & treatment options) or something not mentioned here. Since mange is the worst problem in terms of possible longevity to overcome, and stress to the dog, seconded by staph infection, I would urge you to have the vet examine the skin, do a microscopic exam of the skin scraping, and consult re further options.