That’s interesting. I have never heard that.
But it is quite possible.
“What does not kill me, makes me stronger.”
“Dirty child is a healthy child. “
Making live sterile is causing a lot of problems for many.
Despite liberals always arguing for cleaner air and arguing by citing increase of asthma cases, I have read that the increase in asthma cases is mostly triggered by air too clean.
I have mild asthma and have lived in clean environment part of my live, suffering quite badly, while living in very polluted cities made me a lot better!
Excess retinol contributes to allergies.