This story appears in the February 2015 issue of National Geographic magazine. Currently two species of face mites are known; at least one of them appear to be present on all adult humans.

Demodex mites are tiny eight-legged parasites that mostly live in hair follicles and oil glands on your face, neck, or chest. As alarming as this may sound, they’re generally harmless.

Eyelash mites are tiny cigar-shaped bugs found in bunches at the base of your eyelashes. They’re normal and usually harmless, unless you have too many of them. Also known as demodex, each mite ...