If fleas, Garlic. Cloves of fresh garlic, stuck in a gob of hamburger.
An old hillbilly/farm remedy was to use this one when the dog had bald spots from mange, 1/4 cup yellow sulfur (like is used for drying fruit) and 3/4 cup lard. Rub in often.
One of my Dobermans was allergic to Bermuda grass, so DH dug up the dog yard and laid down 12 inch tiles. Solved the problem.
One of my DD's Chows started digging on her skin till she had a bald, bleeding spot. We washed it well and rubbed Avon's Skin So Soft on it often. New fur came in so glossy DD had the dog clipped and put SkinSoSoft all over her, used a spray bottle and water mixed with the Avon and the dog's new coat was lovely.
Are you sure your dog isn't allergic to corn or wheat? Sometimes dogs can be allergic to the same things people are.