One other think that is often overlooked, is that if you are "histamine intolerant" in the sense that you are lacking diamine oxidase (DAO) enzyme, there is no reason in particular that your mast cells would be unstable so the people connecting it with MCAS and mastocytosis and pushing quercetin and other mast cell stabilizers are really muddying the issue. If you go to an allergist because you are having allergic-type reactions to foods, they will do some blood work and measure your serum tryptase which is a pretty good indicator of the stability of your mast cells. It's not really that mysterious. They are checking for mastocytosis and you can find out that way. Also, if your mast cells were not stable you would be having reactions to other things, which I am not. It's really a separate issue.