I would suggest a grain free wet food. The wet food is all around better for cats than dry food because it increases their water intake and doesn't have as many carbs. I suggest grain free because that is usually the cause of allergies. I would avoid things like corn and soy. Just make sure it says grain free on the label. I highly recommend Wellness canned wet food. My cats have been on it since I rescued them and they are extremely healthy and active. They have never even had a hairball.