I adopted a low histamine diet. Started to eat things like fresh meat and fish, eggs, gluten free and stopped eating citrus fruits which contain histmaine

Cromolyn sodium liquid was the biggest game changer for me. Went from very few safe foods to a relatively “normal” diet again a few months after starting it. I’ve heard good things about the low histamine route also.

For food reactions, cromolyn and a low histamine diet, with a lot of trial and error and journalling. But otherwise, it's a little hard to say, because I take so many medications. My inhaler helps with my MCAS-induced asthma the most.

Not the OP but I went from a “fish allergy” diagnosis to eating most fish again when I got on meds and made sure my fish was relatively fresh. Apparently spoiling fish can have a TON of histamine— to the point where even when it’s still safe to eat for most people, folks like us MCAS buddies will react. I had a strong reaction (hives, nausea, weird taste in my mouth) immediately after eating tilapia one time, but my whole family was fine eating the same fish. It was in the fridge a few days before cooking, but not to the point where it looked “bad.” (When the fish gets spoiled enough that even non-mast-cell-disorder people are affected, I think they call it histamine food poisoning 😳) I have yet to have a problem with any fresh fish. I still avoid tilapia but I sometimes wonder if I could handle it. I’m reading that mackerel/herring/sardines/tuna are typical high histamine culprits, but I’ve had fresh tuna recently no problem. tldr is I guess your mileage may vary, but the freshness of the fish seems to make a huge difference for me!