I am new to this forum, but sadly not new to POTs and mast cell issues. I have been on a beta blocker since being diagnosed with POTs 10 years ago, and largely it has worked well. The real fun started 3 years ago when I became perimenopausal, which set off histamine intolerance and mast cell issues, mainly with cardiac symptoms. AFter taking a year to work out what was wrong with me, I adjusted my diet, tried and abandoned quercetin (CBS issues), muddled through on a few foods for a bit, and about 4 months ago after a few scary heart episodes, ended up on Zantac and Zyrtec. 2 of each a day, which didnt stop the food reactions, but dampened them down and made life manageable. Except for that growing pain in my side and rising nausea, which made me suspect pancreas or gallbladder, and on reading the serious side effect list of ranitidine I stopped both antihistamines cold turkey, and have had a horrible time since. The POTs has come roaring back despite the betablocker, and the food reactions suck. MY spleen is enlarged and I feel as if I am worse. Still, no more zantac or zyrtec for me. My theory is that their anticholergenic effects stopped my gallbladder /pancreas from working properly, with some sort of irritation resulting. I have been checked for gallbladder stones /sludge and there are none. So I am looking for other options, and looking at Parasym Plus. My question is: is it not contradictory to take Parasym Plus for POTS and MCAD at the same time as antihistamines? Dont they work against eachother? Isnt taking antihistamines for mast cell issues going to make it worse in the long-run if a choline deficiency is the root cause? As i dont tolerate quercetin or antihistamines, is there any other treatment I can try?