It would help to know what kind of dog. LWDs (little white dogs) are notorious for being allergic to just about everything. I have a westie and I have to be very careful what I feed him. He is constantly rubbing his face with his paws and on the carped. My vet had 1 client that had to import dog food made with kangaroo meat because he was so allergic! There are meds that you can give him but I would first look into his diet and make sure his food has no corn, byproducts, or fillers.