D.D.
We also had a dog with allergies, she would chew her backside raw or lick excessively. We had a allergy blood test panel done, I believe most vets can do these, which showed the most common allergies. She was allergic to a lot of stuff. So we started her on allergy shots and switched her to Lamb & Rice food. We also had her on those Flea Tablets that we gave her regularly, so we didn't have any fleas. We then switched to Frontline, a liquid flea repelant that you put on their skin between their shoulder blades. After we used that, we discovered that she was allergic to the Flea Bites and that she would go crazy if one was on her. After this discovery we were then able to stop the allergy shots. She was good ever since. Good luck.