@valentinelynx Thank you for your reply and I have some follow-up questions that I hope can be helpful to others as I know there are many on PR who take beta blockers for tachycardia, OI and/or POTS who also go to the dentist.
I have been taking Atenolol for tachy/POTS since 2013 and it worked well but in beginning of 2015 developed MCAS. Although I was hospitalized and it was very severe, I have never (Thank God) needed to use the EpiPen. My understanding is that a BB like Atenolol (or others) could make the Epi not work during anaphylaxis and that it can degranulate mast cells in general.
My MCAS doc (who is very good IMO) insists that I stay on the BB and seems to have a different philosophy. I have also tried to clarify with him which anesthetics (minus the Epi) are the safest at the dentist for someone with MCAS as I have heard not to use lidocaine or any of the "caine" meds but different docs seem to disagree on this point, too.
I assume there are dental meds that are better for ME/CFS patients as well (although it might still differ in MCAS patients) and many people have both illnesses.
Do you have any further thoughts on this? I know you are a doctor, not dentist, but you have a lot more knowledge on it than I do! Thank you again so much.
Gingergrrl, I don't have much experience with MCAS, although my doctor (just started seeing Dr Kaufman at OMI

) thinks I may have it.
Not having any personal or professional experience to help you, I did a quick literature search. There is no consensus, as you have already determined. A number of studies have shown that local anesthetics, lidocaine in particular, can antagonize histamine, or prevent its release. On the other hand, there are apparently case reports of individual patients having histamine-related complications with local anesthetics. It may be that these reactions are more likely if the local anesthetic is not preservative free. The issue is complicated, also, by the fact that the stress of surgery and irritation of tissues itself is likely to provoke histamine release.
My thoughts would be that the safest approach might be to use lidocaine without epinephrine, but be sure that the lidocaine is preservative free. Maybe doing a test dose ahead of time (a small injection of the local anesthetic) and observing for any reaction might help.
If local anesthetics were a major problem in mastocytosis (patients with very severe histamine reactions, of which MCAS is something like a lesser version) then it would be well known in the anesthetic literature, and there is no such information.
I found
this guide (from the UK) that might be helpful (hooray, I figured out how to attach a link!

), and I quote part of it:
"Local anaesthetics
There is no evidence that local anaesthetics of the common amide type should be avoided (lidocaine, bupivacaine, levobupivacaine, ropivacaine, prilocaine) Amethocaine, an ester local anaesthetic found in Ametop local anaesthetic cream, should probably be avoided because it is known to cause localised skin reactions in some patients. EMLA cream (contains lidocaine and prilocaine) is a suitable alternative. There is no reason to avoid epidural or spinal anaesthesia, or local anaesthetic nerve blocks."
From:
https://www.rcoa.ac.uk/system/files/MASTOCYTOSIS-2014_0.pdf
Please discuss with your doctors and dentists, as I can't give real advice as I am not your physician.
Hope that helps. Good luck!