What's so interesting is that it gradually became a fact of life and I never stopped to think of it as odd. Assumed it was allergy-related but now I'm seeing a bigger picture thanks to you all...

Yes!! For years!

I think it could make sense as a nervous system or immunological response. Someone posting here called it a certain type of rhinitis, I think they were on to something.

Been there. Was told it's "physiological", and somewhat dismissively, to boot. I sneezed twice while typing this 😅

Doesn't make sense it's a fibro thing.. have you tried treating it with antihistamines or going to an ENT?