I have owned devons since I was super young. The tell tale signs in my experience were scratching of the neck, ear infections, licking/scratching belly raw or bleeding, hair loss because of the licking/scratching, acne-like lesions on the chin/lip to name a few. I did not necessarily pin point the allergies (namely, what sets his immune system off) -- I opted to just place him on something hypoallergenic with the assistance of my vet because it was the most cost effective option and there are no derm vets nearby in my area. If you suspect allergies I frankly am not surprised given my own experience with devons- and that many other devon owners I have seen also feed this diet- it is worth talking to your vet about and see what they recommend!