allergies. He wound up with ear infections, cysts, vomiting profusely, and a bacterial infection in his tummy. He was a wreck. The RX food is expensive but considering how much the vet and a two day stay in the hosp. cost, and how miserable my baby was, I will pay for the food. Also, if he does well on the food, don't make the mistake I did. I decided that I really wanted Brutus on a better food than the RX, so I tried a hydrolyzed blue buffalo brand and what a mistake. He wound up scratching and with cysts and an ear infection again. Back on the RX food immediately and will not ever take him off again.