@zuperhero -- going through a raft of dysautonomia testing, I finally arrived at the last one, the one I was sure would not be an issue for me. But the tryptase came up high (14.5 in my case). As you know 20 ug/l is indicative of Mastocytosis, but under that cut-off it seems like tryptase measurements can mean something in regard to MCAS or not. Most people with MCAS have normal or close to normal tryptase tests, from what I understand.
My dysautonomia doctor immediately put me on a two week trial (and this is pretty standard as a diagnostic I believe) of famotidine (Pepcid) and fexofenadine (Allegra)--two OTC histamine blockers. I had no allergic issues of which I was aware, but after a couple of days on these guys, I felt better. Not all better, of course, but noticeably so. After ten days, I took a break, because I was in some disbelief about whether these meds could be really helping. I did not have anything that made me think or feel--MCAS. But the day off was a revelation--I felt awful for a few days, but improved steadily back on the drugs.
I also had another set of tests routinely done when there is a MCAS red flag, like 24 hour urine prostaglandins and histamine, but the tests are pesky and mine were mishandled and resulted in no new info. My doctor did not seem to feel that those results were nearly as important as my response to the histamine blockers.
I have since found Natural Factors Bioactive Quercetin EMIQ, which in relatively high doses, I can take in place of the famotidine. Like you, I have experimented with low histamine diet and introducing high histamine foods and have noticed absolutely nothing one way or another.
Another diagnosis? Hurrah! Right? In any case....good luck with this.
