You can't make a CLEAN environment. Our immune system wasn't built for that.
It all boils down to the concept of hand sanitizer. It keeps "BAD STUFF" away. Which makes you unprepared to handle it when the "BAD STUFF" gets you no matter what. I rarely wash my hands, outside of them being filthy with dirt, crap or noxious chemicals. I do that specifically because I want my immune system challenged every day.
"That which does not kill me makes me stronger. At this point I can bench press a '68 Buick."