I was with you on car crashes & lead paint, but how do allergies come from a wealthy society? Or do you mean that only in a wealthy society are there resources/medical infrastructure available to diagnose them?
It would be a reference to the hygiene hypothesis, that being too "clean" leads to lack of exposure to things we evolved to encounter in the environment (worms mostly) which causes the immune system to go a bit wrong, causing allergies and autoimmune conditions.
Ah, okay. I've heard that before but thought it was basically fringe science. My assumption has simply been that allergies always existed like this, but those with more severe ones died off very young and the concept of "allergy" somewhat non existent. I'll admit the possibility though, ever if I'm very reluctant to lump it together with more obvious wealth-associatated issues.