Yeah, no one wants to fund those sorts of studies, because they would produce uncomfortable outcomes. Similar things are observed in the Amish.
Previously I would rotate through antihistamines because nothing else worked for me, and I would suffer heavily without them. Not sure what I have done aside from cleaning up my diet and being mostly meat based over the past 3 years. Also haven't been sick since the end of 2020, which would be an annual guarantee before that. I still wonder if there were residual effects from the shot that many years ago which eventually wore off.