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!)"."
While the widespread nature of these mites was assumed, all the censuses that had been performed were based on visual counts, so Thoemmes and Dunn decided to search for the mites’ DNA in their volunteers. This was a fairly easy process because when face mites die, they release an incredible amount of DNA on their host's face. This of course means that you not only have live mites on your face, but also the remains of their long-dead peers.
Of the 253 volunteers the researchers recruited, they saw the actual mites on 14 percent of them, and when they checked for mite DNA in 19 of their volunteers, they found that 100 percent of them had it. The team is publishing the results of the study in the journal PLOS ONE.
Something else they found was that while 100 percent of the adults they searched had face mite DNA, only 70 percent of the 10 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."