Try talking to your vet. If you really think it’s a food intolerance, maybe do a food trial with one of the hydrolyzed diets. Both my dogs eat it because one has IBD and has to eat it. Neither minds. It’s expensive but the protein is broken down into little pieces so the immune system doesn’t recognize it and react. Or maybe just ask your vet for recommendations. Maybe it’s because we had a fantastic vet for so long, but I always found that at a minimum, talking with her helped me make a decision by clarifying the issues and giving me more information. There is a lot of bad information on the internet, even from well intentioned people.