Exposure, especially kids. Also food it I had to guess.
It seems that we are shielding ourselves ever more from exposure to nature. Which has tremendous benefits, but allergies seem to play into that.
As for food, I have now seen too many people cure themselves from hayfever and other allergies by ditching carbs, or other significant dietary changes. No accident if you ask me. And would line up somewhat with industrialization of food production post 1800 or so.
It seems that we are shielding ourselves ever more from exposure to nature. Which has tremendous benefits, but allergies seem to play into that.
As for food, I have now seen too many people cure themselves from hayfever and other allergies by ditching carbs, or other significant dietary changes. No accident if you ask me. And would line up somewhat with industrialization of food production post 1800 or so.