StarSloth#MCAS people: can you tolerate the following foods? Yes, partial/small amounts/when not in a flare, not at all, whatever details that you want to share.
Potatoes
Soybeans
Soy derivatives (sauce and other soy products)
Red beets
kMy MCAS goes wild with cross allergies to birch and grass
Soy and derivatives - now never. Huge reactivity even to micro contact (scent). Cannot do traces of.
Potatoes - lost them in a bad flair (2024) but they were one of the first foods I got back once I started to stabilise
Beets - lost them in a bad flair and they were one of the last foods I got back. I tolerate small amounts of cooked beets* now, on good histamine days. I have not wanted to try them on a bad one
Food became a lot easier for me after i started taking birch and grass allergy drops. But it's the kind of intervention where, if it's the wrong one for your MCAS situation, will make things very very wrong. Meds are hard for me for a lot of reasons, and I'm grateful these were the right choice for me. I hope you're also able to find the right approach 
@forestfjord I am on 20mg desloratadine + 10mg hydroxyzine + 10mg Montelukast daily, and together with dietary restrictions that's worked fairly well, but I am less worse off than you and many I think. The only things I am 100% sure I can eat are rice, iceberg lettuce and cucumber, zucchini, but I have a grading scale of categories of food I can usually eat, and some of those include small amounts of normally nope foods (example: a few slices of pickled red beets are most often fine!).
@forestfjord but I am not well managed foodwise since I don't have the energy to cook and A aren't as well versed in my needs (he tries), so I am lowgrade itchy a lot of the time. I need to get Not Itchy so I can verify 100% if the heart med causes a reaction or not, that's a short term goal.
@forestfjord these food questions are more long term though. I've started wondering if I need to downgrade potatoes (nightshades!) to a lower category (ie one I stop eating earlier in a lowgrade flare), for instance. Similarly I've wondered if I can upgrade soy to a higher category (from inedible to lowest edible, like small amounts of tomatoes to compare directly, small amounts of soy seem fine when I am in a good period?)
Another resource rec : what the bleep can I eat dot com (or similar)
It has a lot of filtering options, and a lot of info about where and how they make their lists
It helped me figure out that my biggest problems were cross allergies, then histamine storage (leftovers; fermented), then histamine liberators.
Itchy is hard. Have you tried cromolyn? There's a German pharmacy that sells compounded MCAS meds. I think I still have a pdf of their MCAS menu if you'd like an email
@forestfjord cromolyn isn't available in Sweden, so no. And yea, for me it's a different order, but also, I am developing my own system. Some things I tolerate well but I never eat them in large quantities (raspberries), which probably affects the outcome. I am currently howling with laughter because my partner is very frustrated that I won't eat eggwhites, only the yolk, and I detest licorice, and the list you emailed answered why. I haven't actually figured out why I don't like them before now