It is believed that all humans have Demodex mites somewhere on their faces.  It is only when they become at the infested level that we would be aware of them.  I can speak from...horrible...experience.  At the Computer I could feel them crawling up and/or down my neck.  They were in my eyebrows enough to make them itch.  They would crawl on my face, usually at the base of my nostrils.  And, of course, the crunchy stuff on my eyelashes along with the burn and the itch.   I used a substantial routine of all Clinidex products and eventually calmed them all down.   But every few months, I can tell they are multiplying faster again.  Gross....but real.