Mine turned out to be what a previous doctor had years prior brushed off as, "You have IBS. That's usually caused by anxiety. You should learn to meditate." Green leafies caused the same reaction, and are also an allergen.
Yeah, no, doc, I had FOOD ALLERGIES and I might have had relief a decade earlier if you had RUN A TEST instead of patting me on the head and being condescending...
I had the kind of "IBS" where I was in so much pain it could eclipse my endometriosis pain; my stomach would distend so much I looked pregnant and my pants didn't fit; and, well, the plumbing was either clogged or on full blast. And lots of painful, trapped gas. I drank on average four ginger ales a day trying to control it because nothing else helped. I still drink a lot of ginger ale but on average about one a day now. I wonder if the remaining issues are a food I haven't eliminated yet, but it's a world of difference from how I was!