[theBCnut]

They could be sensitive to a particular ingredient, but if it is all of them, I would expect it to be a grain mite issue or something environmental. If it is a sensitivity to a particular ingredient, it can be any ingredient that has protein in it. The usually culprits are chicken, beef, grains, soy. You may want to take your current ingredient list with you and find a food that is about as different as you can get.