My Vet Says That My Dog Has Food Allergies But The Special Food Doesn’t Seem To Help What Can I Do That Will?

We have been giving him only the natural duck and potatoe that the vet said to use and the shampoo, but he still chews his feet raw and scratches all the time. Has anyone else had this problem and if so what did you do to help your dog? He’s to young to leave on prednisone.