There are a few genetic factors that can contribute to it. I’m lucky enough to have most of them, so it’s been a journey figuring this out. What got me on the right track was trying a low histamine diet for a week, and all kinds of not-quite-allergy things I had experienced my whole life began to clear up.

The exact list of foods varies a bit depending on the resource, but here’s a pretty good one.

You might want to look into histamine intolerance.

Foods like that can elevate histamine levels because they contain histamine, and some people are less efficient at flushing them out of the system (either during or after digestion), so it results in allergy-like symptoms even without an allergy per se.