Hello I have a 7 month old male GSD. He has been eating blue buffalo chicken puppy grain free. I started him on this food and then my vet told me to get him off grain free and switch him to royal Canin Germans shepherd. Immediately after switching him to this he would hardly eat and would itch constantly. I switched him back to the blue buffalo chicken. And the itching has went down quite a bit. But still itches behind his ears every now and then and has lost some hair behind his ears from scratching, most of it was from when he was on royal Canin. Is it chicken a common allergy? Looking for some possible guidance or experience.