> The fact that you have alternating diarrhea and constipation means that you will likely test positive for both hydrogen and methane with a lactulose breath test, meaning overgrowth of both bacteria and archaea in the small intestine. All of the things you mention are related to that.

That might be possible, but all digestive symptoms disappeared pretty much completely within two weeks of a low histamine diet.

My diet does not appear to be FODMAP although there might be a little bit of overlap.

I find ginger super helpful, I drink ginger tea, put ginger in my food, add ginger powder to my soup, if I think I might get a migraine sometimes I'll take Gravol ginger extract. It naturally contains quercetin which is an antihistamine. Some studies suggest ginger can be as effective as some antihistamines for allergies