There's a lot of evidence indicating that the hygiene hypothesis is not accurate or at the very least not the whole story. The old friends hypothesis suggests

There's a lot of evidence indicating that the hygiene hypothesis is not accurate or at the very least not the whole story. The old friends hypothesis suggests that exposure to certain pathogens is just as important or more so. Also microbiomes may play a part in things as well. Everything is a bit up in the air, tbh.