It's an interesting subject, and one that's caused me more than a little trouble over the years.
I'm not convinced by any means, but I'm suspicious that early childhood programming has a lot to do with it. A sensitive and intelligent child can pick up on all sorts of parental ramblings, and start to fear all sorts of things. "Sitting in a drought will give you a bad back." And it does - despite the fact you were hanging over the side of a sailboat in a force five for hours, and it left you felling like Superman. A far-fetched analogy, but you know what I mean.
Migraine is horrific, and so often comes at a time that tallies with long term worry. So counter-productive. Yet something seems to not just trigger the onset, but actually
plans it. (a recent paper )
That some
thing is very real, and I confess multiple sentience is a hobby-horse of mine, but I think there's a lot of sub-processing going on based on reasoning that has no place in a modern world; a world filled with new and exotic molecules. 'It' hasn't a clue how to react productively.
I'm now in a situation where I can't touch wheat. Yep, and that includes best malt

Not even a little bit. I'm scared stiff of washing up liquid, and using cheap soap makes me ill within an hour. There was a hint of it when I was c 40, but it went away after extensive tests by AVM Cook, head of aviation medicine. They didn't find a thing wrong, but the mystery took its toll on my career despite being very transitory.
I was in my early 60s when the main issues started, and the first experience would have left me on the floor of the flight deck. It was
totally disabling for 10 of the 30 mins it lasted.