Especially in the last years, the hygiene hypothesis is not about a lack of immune training against harmful microbes, but a lack of encounter of so called old f

Especially in the last years, the hygiene hypothesis is not about a lack of immune training against harmful microbes, but a lack of encounter of so called old friends, harmless microbes. https://www.pnas.org/doi/10.1073/pnas.1700688114 https://www.pnas.org/doi/10.1073/pnas.1700688114