I have a theory: the beard acts as a virus/bacteria catcher.

Prior to growing the beard, I was good for some form of illness about once a quarter. And, without fail, a trip to the airport was a certain harbinger of coming down with some form of unidentifiable sneezy coughy sore throat crud.

I grew a goatee about a year ago...haven't been sick since. Not once, and I am travelling far more frequently.