Our vet wanted to do a bazillion tests for allergies. My poor lab was almost bald and so itchy she was not even able to sleep.
I took her off of all commercial food, I cooked her rice and ground turkey for weeks. After her skin was basically healed, I gave her some oatmeal, and flash! Red - skin - rash breakout! So no more oats for you little doggy. Then I tried some fish, no problemo. I tried carrots, good. Sweet potatoes, no prob. Then a friend told me they make a sweet potato/fish protein food. It is more expensive than the other food I was feeding. But I saved the $500+ that the tests would have cost, the $240 that each office visit seems to cost and the $200 in meds they always say she needs.