It could be something similar to the Hygiene Hypothesis [1]. Basically the body and immune system co-evolved in an environment with a higher level of dirt, ger

It could be something similar to the Hygiene Hypothesis [1]. Basically the body and immune system co-evolved in an environment with a higher level of dirt, germs, and injury. Our immune system is designed for that more hostile world but now we live cushy sterile lives free from injury most days. In summary, there is a mismatch between the environment the immune system is designed for and the one it currently finds itself in. [1] https://en.m.wikipedia.org/wiki/Hygiene_hypothesis https://en.m.wikipedia.org/wiki/Hygiene_hypothesis