Just going by what the vet said. We took him in when he first got him. He had really weepy eyes and was snorting way more than a reg pug should. He asked him what he was eating. The previous owners had him on Purina. We, of course, switched him right away. All of his symptoms cleared up. When we went away last year on vaca, he stayed with some friends of ours. I didn't think to tell them about his allergy because we were providing them with his food anyways. They ended up giving him some crap treats that were corn based. Same thing started up again. His eyes started "crying" and he got all snuffly. *shrug*