[Lovetodream88]

Well food allergies are rare so it more then likely is environmental. If it is food allergies even if the food you think the allergy is to is supposed to not be in a food there could still be traces of it. Dog food is created in a plant with lots of different types so even if your feeding a food with no chicken, it could still get some chicken it it because its in other foods made at the plant. The only way to make sure there not getting any of the food is by either a prescription food or to home cook which requires supplements and a recipe from your vet. I would take him to the vet and see what the vet thinks.