[DRN]

I agree that you need to rule out allergies and fungus. Even with a culture, you can't be sure about fungus because it may or may not come back positive (we all have bacteria, fungus, etc., in our bodies - the point of the culture is to tell us if we have too much). I would ask the vet about a trial of antifungals and antiibiotics, but not at the same time.

This is just a gut feeling, but I would also consider something for anxiety. It's not uncommon for dogs to initially have a good reason for licking and chewing (fungus, infection, allergies, a foreign object), but after it resolves they will continue to chew. It's a doggie form of Obsessive-Compulsive Disorder. I have cockers and they do this quite a bit. I suggest asking your vet about Benadryl, melatonin, or the pet formations used for dogs who are afraid of thunder. It's really the same phenomenon even though it seems completely different.