Wesley Clark, you’re forgetting the Hygiene Hypothesis, it’s precisely why a lot of people are getting sick now in first world countries with autoimmune diseases, inflammatory skin conditions, asthma, allergies, etc. We are too clean and we are also not exposed to all the parasites we were all along our history on this planet that also helps modulate our immune system. And then you have the diseases of affluence like obesity and type II diabetes, if you have an office job or something it’s pretty easy to get by in this world with almost no exercise.
[quote=“pool, post:21, topic:719787”]
Wesley Clark, you’re forgetting the Hygiene Hypothesis, it’s precisely why a lot of people are getting sick now in first world countries with autoimmune diseases, inflammatory skin conditions, asthma, allergies, etc. /QUOTE]
Another vote for this being a potential cause of asthma and allergies in younger people.
I will say though, that you can’t cure asthma or allergies retroactively by being a terrible housekeeper. I’ve experimented with this. 
(Ok, not intentionally, but still, wouldn’t it be nice?)
My mom was a stay-at-home mom and had the German housekeeping standards of her paternal family. I swear I saw her wax the baseboards. She was a little surprised post-divorce when she went to work and college and the housekeeping “slipped” and my allergies/asthma remained the same. I’m still sad knowing that having a the canopy to the French Provincial on the bed of the white-and-gold bedroom set like every other little girl I knew wouldn’t have made any difference. 
You’re also forgetting pollution from industry, cars, etc. There are organic mercury compounds in some kinds of fish now. Most of those compounds got there from things like coal-fired power plants that didn’t exist for most of human history. There have been cases in Japan where people had health problems due to exposure to methylmercury from a chemical factory. People used to be exposed to lead from automobile exhaust. Tetraethyl lead didn’t exist before the 1920s, so nobody was exposed to it before that. We know that exposure to lead can have bad effects on health.