I discovered that whitener in tooth paste was the cause of burning and irritating tongue/ mouth. I used Sensodyne tooth paste for years. My dentist suggested I try a different toothpaste just to rule it out as a cause. When I stopped using it did resolved. I used Colgate regular toothpaste. Then I started using whitening toothpaste. Symptoms returned in a big way. After ruling out all other possibilities as listed in your comments, I suspected toothpaste again so returned to regular no whitening and now symptom free! I noticed they had added Whitening some years back to Sensodyne toothpaste which started all those symptoms. I hope it maybe as easy a solution as this for you.