Long, long before we two-legged skin creatures roamed the earth, there were all kinds of microbiota (such as bacteria, fungus, yeast, etc.) living their little buggy lives and performing their special tasks. The human creature has been living and growing with these microorganisms as part of their physical make-up this whole time and yet not only do we consider those little guys to be unimportant, but we take active measures to kill them all on a regular basis.
Collectively, we may have forgotten that we NEED them as much as they need us (maybe more so). The microorganisms that live on the surface of our skin and inside our gut are important for our defensive line, our immune system, detoxification, elimination and a slew of other things we rarely give them credit for.