There are at least 48,000 species of mites in the world. Thanks to a new study released this week, we now know that at least two of them live on human faces.
Study leaders Megan Thoemmes and Rob Dunn and their colleagues from North Carolina State University found that every adult in a small American sample had face-mites on their faces-something that has been suspected for a long time but never confirmed officially.
Face mites were discovered in 1841, but weren't described until a year later by German dermatologist Gustav Simon, according to National Geographic. Simon had been looking at acne spots under a microscope when he noticed a "worm-like object" with a head a legs.
After extracting it, he pressed it between two slides, and saw that it moved. A year later, Richard Own gave the mite its name, demodex, from the Greek words "demo," meaning lard, and "dex," meaning boring worm.
Two species of mites can be found on humans: Demodex folliculorum (bigger, round-bottomed) and Demodex brevis (smaller, short-bottomed), according to National Geographic.
"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!)," wrote legendary mite specialist William Nutting back in 1976, according to National Geographic.
In 1903, researchers said in a study that they found mites in 49 out of 100 French cadavers. In 1908, mites were found in 97 of 100 German cadavers. Most studies since then have fallen in the range of 10 to 20 percent, but they were all based on visual counts.
People can apply cellophane tape to their skin to pull the mites off, scrape an oily patch of face with a tiny spatula, or even by plucking eyebrows and eyelashes. Mites aren't easy to get rid of as they live in our pores. They can also aren't evenly distributed, according to National Geographic.
Thoemmes decided to search for their DNA, which has never been done before. Mites release a lifetime's worth of waste when they die, which contains their DNA. This gives away the presence of the mites even when the creatures are actually still hidden.
She created a test for Demodex DNA and recruited 253 volunteers at "Meet Your Mites" face-sampling events.
"We had really good responses," she said, according to National Geographic. "People act grossed out at first, but they get excited when they see the mites under the microscope."
She saw actual mites on 14 percent of the people who volunteered, which is in line with previous estimates. She also checked for mite DNA in 19 adults, and found it on all of them.
Thoemmes also sampled ten 18-year-olds and found Demodex DNA on just 70 percent of them, which helps prove that mites become more common with age.
Results were published this week in PLOS ONE.