I remember reading or hearing somewhere that everyone has microscopic lice living in their eyebrows, or upon their eyelashes, or something like that. If this is true, how many other microscopic parasites are hitching a free ride on the average healthy human body? And when I get a random itch, is it one of these pesky little things biting me? I’m not exactly sure how much ignorance I want removing here, but at least I don’t have to look at any pictures! 
**Life On Man **by Theordor Rosebury, originally published in 1969 but re-printed many times since (there may even be a second volume out), will tell you more than you want to know about all the disgusting things that live in and on the human body. Yuch! It is a fascinating book, however.
There is more not-you in you than there is you. Like, by a lot. Guess what percent of the cells in and on you are actually you.
Go on. Guess.
No, lower…Lower…Still lower…Come on, really lowball it. Nope, lower yet.
10% Yes, you read that right.90% of the cells in “you” actually belong to microbes.
Most of our hitchhikers are beneficial, many of them are neutral, only some of them cause illness. Here are some pictures. The mites you’re thinking of are #7: Demodex mites.
More cites for that number. Since I know you won’t believe me.
Sleep well! 
Keep in mind, though, that the vast majority of the cells you’re carrying around are bacteria, and the average bacteria cell is much much much smaller than the average human cell. For whatever that’s worth.
WhyNot snippet:
There is more not-you in you than there is you.
Just perfect!!
That, plus they are leaderless and poorly organized. They don’t frighten me.
Weird Al: “I wish they’d pack their tiny little bags and move away.”
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Colibri
General Questions Moderator
That’s what’d interest me – how does that work out body mass percentage wise? Or, if I were to collect all the not-me parts of me, how big of a pile would I get?
But, wait, there’s more!
My high school Biology I teacher had just finished a course in Parasitology. Not just those little, invisible critters that plague us. But the more “interesting” ones–like guinea worms & the organisms that cause trichinosis. (Not Wikiíng for further data–because I don’t really want to know more.) And not just human parasites. She’d spent time going through organs at the Port City Stockyards for class credit.
We enjoyed learning because of her enthusiasm & I gladly signed up for Biology II. However, during the intervening years, she had complications from pregnancy & dropped out of teaching. So we ended up with a dread Coach Teacher. (The ones who get tossed a few extra classes to fill up time left over from their **real **jobs.)
The term “parasite” can be a bit misleading, here, since most of the critters that live in and on us are completely harmless, and many of them actually help us (aiding in digestion, for instance). “Parasite” usually refers to relationships where the host suffers in some way.
It’s worse than that: Officially, the few extra classes are their real jobs. Many school districts have rules that require that coaches be selected from among the teachers, so when they hire a coach, they have to officially hire him as a “teacher”, with the understanding that he’ll coach sports in addition to his official duties.