My pug doesn't have food allergies but my bulldog does. I took her to the vet and he put her on Hills z/d dog food. I liked it a lot. It was expensive and we had to have a prescription to buy it but her earaches and skin problems vanished.
Other dog owners I've spoken to have had more of a problem dealing with food allergies and have had to try several food types. Several people suggest feeding raw but my vet says that feeding raw is not a good idea because the raw meat that we provide is not the same that a wolf would eat in the wild and it just isn't healthy for domesticated dogs. Good luck!!