How Researchers Find Symbiotic Mite DNA on our Faces

This is a passage from The Year of the Mite that describes a presentation I attended in March 2015 by entomologist Michelle Trautwein called “Meet Your Face Mites: A Story of Discovery, Evolution, and Intrigue.” To learn more about the work of Michelle and her colleagues, just Google “Mites Having Sex on My Face” and check out the video.

Michelle focused on two species from the genus Demodex that show up in our faces: D. brevis and D. folliculorum. They live in hair follicles and eat sebum, small quantities of face goop. So they are scavenger mites, and not true parasites. Unlike my gallinae, they don’t need to bite to eat. So they don’t hurt.

Michelle described the old methods for collecting face mites: tape and a microscope. Not that effective. Pretty much how we try to collect D. gallinae. Using those methods, somewhere between three and ten percent of humans appeared to have face mites.

Then she described the methods she and her fellow face mite researchers developed: They collected material from the faces of willing subjects using slides covered with something like super glue. They used Polymerase Chain Reaction to sequence the DNA from people’s faces. Then they isolated and identified the DNA that is particular to the two Demodex species. And more: they broke it down to which subspecies of face mites have been passed down from mother to child for centuries in different parts of the world. These scientists can tell where your ancestors came from by the genetic sequences of the mites that live in your face. And using these advanced detection methods, they found that 100% of human beings have mites living in our faces.

One hundred percent. This means you.

Pretty fascinating stuff.

Courtesy of Michelle, I now have a whole different answer to the question, “Why are mites so hard to find?”

Answer: The old methods don’t work very well. You need to sequence the DNA on your skin and look for DNA that is unique to mites. You’ll find the DNA of scavenger face mites, for sure. And if you are infested with parasitic chicken mites, you’ll find that DNA too. And if your doctor isn’t using super glue and PCR to check you for mite DNA, they just don’t know what is going on.

So now it’s my turn to ask a question: If it’s worth sequencing the DNA of scavenger face mites, purely for scientific interest, isn’t it worth collecting and sequencing parasitic mite DNA from people who have been suffering for years? Wouldn’t it be good to know for sure what is happening, so we could help these people? If you are a physician or a therapist with a patient who is being bitten by something they cannot see, this question is for you.