Of the 48,000 species of mites, two are known to live on
human faces. And even more than our beloved pets, they’re the animals we spend most of our lives with.

A recent study led by Megan Thoemmes and Rob Dunn
from North Carolina State University in the US looked at a
small sample of American adults and confirmed what had
long been assumed - that 100% of them had mites living on their faces.

"They live in our hair follicles, buried head-down, eating the oils we secrete, hooking up with each other near the surface, and occasionally crawling about the skin at night," says Ed Yong at National Geographic . "They do this on my face. They probably do it on yours."

These worm-like mites, of the species Demodex folliculorum and Demodex brevis, were first discovered in 1841, and described a year later by German dermatologist Gustav Simon. Simon found one and extracted it as he was examining his patient’s acne spots under a microscope. "Scientists have since found Demodex in every ethnic group where they’ve have cared to look, from white Europeans to Australian aborigines to Devon Island Eskimos,” says Yong.

In 1976, legendary mite specialist William Nutting wrote, “One can conclude that wherever mankind is found, hair follicle mites will be found and that the transfer mechanism is 100% effective! (One of my students noted it was undoubtedly the first invertebrate metazoan to visit the moon!)

Something else they found was that while 100 percent of the adults they searched had face mite DNA, only 70 percent of the 10 to 18-year-olds they tested had it. "This fits with what earlier studies had shown - the mites seem to become more common with age,” says Yong . "They’re rare on babies, more common on teenagers, and universal in adults. No one really knows where we get them from. But the fact that some teens aren’t colonised suggests that we pick up these creatures throughout our lives."

http://pda.sciencealert.com.au/news/20142908-26088-2.html