Comment by simondw

> Exposure to regular levels of background bacteria and virus keeps our immune system tuned

> While the mask likely does not protect you from background virus and bacteria

If you believe the second statement, why does the first matter?

> it can host all sorts of new growth right against your mouth and face

Have you seen any studies on how quickly harmful growth can build up? I'd guess this to be pretty harmless if you change the mask regularly.