My dog has multiple food allergies-after many years of trial and error we've settled on Iams Sensitive Oceanfish, Barley and Rice. She seemed to be allergic to chicken and that is in almost everything! When we were trying different foods the vet said it takes awhile to get the old food out of the system-like twelve weeks or so. Bailey is also on Benedryl when she just can't stop itching. Good luck.