Those are great examples!

However, I’m not sure I agree with that allergy hypothesis. The histamine reaction is associated with IgE. This immunoglobulin is associated with parasitic response. A lack of childhood exposure actually higher correlates with higher incidence of allergies and asthma. The theory that has developed from this is that lack of stimulation leads to hyper reaction later when exposed to allergens.

This is all posited by the “hygiene hypothesis”: https://en.m.wikipedia.org/wiki/Hygiene_hypothesis

There is a lot of supporting evidence to go along with it. As well as studies inspecting the impact of gut micro biome.