The list is long...he was on Kirkland brand, Costco, when we got him. We bought merrick puppy formula, no problems. 1st vet had never had a Frenchie in her practice before but when I scheduled his 1 st appointment I asked if they, 4 vets, had treated or even seen Frenchie before. Yes we have tell tale sign was when we son and I walked in with Capo everything stopped they all wanted him. We left after coccida test was positive and we were told he would grow out of it. 2 weeks later after each poop there was a trail of blood from his anus. That vet said merrick was to high in protein she wanted him on adult formula. 2 nd vet 3rd food royal canin found out his allergic to soy, then hypo allergenic Royal canin still itching, then beef and rice and Flagyl, then 3 red vet allergist purina hypoallergenic back to 2nd vet now on Canidae 8 ingredient seafood and vital pet fresh salmon grain free. We thought we found the right food still soft serve, blood is hit and miss. When he's excited he has diarrhea and urgency. His coat is beautiful not a hot spot or sore to be found. His face around his mouth gets red bumps then he itches