All the these posts are very interesting. I think the idea that MCAS patients are NOT supposed to be on Beta Blockers is of extreme importance to this subject. Also to comment on Sue1234 post I have noticed a significant but definitely slow improvement in symptoms now on the MCAS/ (formally MCAD) regime. I must say though that I am still trying to find the best H1 fit for myself as Allegra makes me super duper hyper and my heart race and Claritin puts me to sleep. I have found that I think so far Zrytec seems the most mellow of the name brand bunch. Also On the MCAS forums they say that Zrytec is good for palpitations- I don't know how based in actual truth this is so don't quote me on it but I think I've found it to be true for myself for sure. Also I should comment that Claritin helps me immensely with Tachycardia and that is something i noticed pretty immediately when one morning i was unable to take it until much later than i normally do and was really struggling with a racing HR. And then as soon as I took the Claritin it settled down immediately. This would actually make sense because in MCA, if your having an episode your body is filling up with too many Histamines, so think of it as the beginning of an allergic reaction. Well what happens in an allergic reaction? Are hearts start to race, are bodies flush, we get an over reaction of our sympathetic nervous-system. Also I have seen several quotes from Dr.Grubb's patients saying that they were told Wellbutrin was the AD of choice for this specific subtype. So again, I am not a medical doctor but I have found for myself so far it seems to be doing a pretty good job compared to the others i have tried. (which i have tried a bunch!) ex. Lexapro was too activating/ Celexa made my dysautonomia 20times worse/ Prozac worked for a bit but then made my Ehler-Danlos go crazy giving me hyper-extension of my muscle's. (which pretty much feels like you can flex your muscles until they snap!!!) The thing is I think most Doc's are afraid to try Wellbutrin on us because its so activating, so I'd love to know the science behind why this drug in particular has the reaction that it does in MCA patients who normally present with extreme hyper-sympathetic tone. Also finally, most people on the MCAS boards swear by Singulair and say that that was the game-changer for them in over all better control of symptoms. My Autonomic specialist, once he realized that i had Mast Cell Disorder he asked if I had ever tried Singulair, and I had not and wanted to do some research on the matter before i went down that road. I have a follow-up with the Doc this Monday so I think now that i have done my homework I might give it a try.