Brita,
Your doctor may have a point, but I don't think it's very strong for you've not been on high antihistamine therapy for very long.
When I saw my dermatologist the other day she showed me a brand new article published by some Brazilian doctors on the MC involvement in the bocal tissues.
I have a feeling that it's the masto behind your problems in that there may be degranulating going on inside your mouth and this may be causing increased inflammation and problems! It may not be directly a result of masto, but it may be connected in that one is tiggering the other.
Start googling mast cells and oral related subjects and see what kind of research you come up with and send it to your dentist. It may end up not only educating him as to the involvement of the MCs in the mouth, but it may help your specific case as well.
As to upping your meds, YES! You have three issues going on there - one is the anxiety we all get with dentists. two is the stress upon those tissues in his working there and three is any bacteria or enzymes he may end up introducing into your system. Any one of these three may end up causing extra activity. You may even want to take something like vallium if you get extra nervous!!
Use the REMA protocols as your pre-medication routine for they were designed for risk situations like this. I know it seems ridiculous to compare it with a colonoscope or CT scan, but you've got to remember that for the great majority of people out there, dental proceedures cause the highest levels of anxiety in people and just that alone is enough to put you into outer space!
Lisa