My mother had a problem quite similar and it lasted on and off for almost 2 years. Doctors kept giving her different reasons and medications (even steroids), none of which provided permanant relife. She was talking to a distant relative who had also had a similar problem, and found out that it was whitening toothpaste. Even the smallest amount of whitening in the toothpaste caused her to have it come back. Must have been an ingrediant in the whitening. Anyways, 2 weeks after she stopped using anything like that, she has never had symptoms again. It's worth a shot. Hope this helps.