Adding to this (not wanting to engage on the main post): allergies have been increasing also because our environment is getting more polluted by the day. Unfortunately, allergies not being known and detected earlier means that good studies on the “real” increase of allergies are really hard to make. Same with mental health issues, that “didn’t exist” some decades ago (people either could bare it or committed suicide, that was incredibly often covered up by the family because it was shameful)