It might give you the creepy-crawlies, but you almost certainly have tiny mites living in the pores of your face right now.
They're known as
Demodex or eyelash mites, and just about every adult human alive has a population living on them.
The
mostly transparent critters are too small to see with the naked eye. At
about 0.3 millimeters long, it would would take about five face adult
mites laid end to end to stretch across the head of a pin.
"They look like kind of like stubby little worms," says
Michelle Trautwein, an entomologist at the California Academy of Sciences in San Francisco.
Demodex
face mites got their name from the Greek words for "fat" and "boring
worm," but they're not really worms at all. They're actually arachnids —
related to ticks and, more distantly, to spiders.
Michelle Trautwein, an entomologist at the California
Academy of Sciences in San Francisco, tested more than 2,000 people and
found DNA evidence of face mites on every single one of them.
Josh Cassidy/KQED
Trautwein studies our relationship with these microscopic
stowaways by looking at their DNA. Her findings suggest that people in
different parts of the world have different face mites. "They tell a
story of your own ancestry and also a story of more ancient human
history and migration," she says.
But before she could tell that story, she needed to find the mites.
"We
use a little spoon and scrape it across the kind of greasier parts of
someone's face, which isn't as bad as it sounds," Trautwein says.
Once the samples have been collected, she takes them back to the lab to look at the genetics.
Trautwein
has tested more than 2,000 people, including tourists from all around
the world that make their way to the California Academy of Sciences. And
she's found DNA evidence of face mites on every single one of them.
"No
one is thrilled at the initial notion that they have arachnids on their
face," Trautwein says. "But people are often curious — even in their
revulsion."
But how could these creatures live on so many people and still go unnoticed?
Our
skin is mostly covered by a thin layer of peach-fuzz called vellus
hairs, with a few notable exceptions such as like the palms of our hands
and feet. The shaft of each one of those tiny hairs grows out of its
own follicle.
Face mites —
Demodex folliculorum and
Demodex brevis — spend their days face down inside your hair follicles, nestled up against the hair shaft, where you can't see them.
They eat sebum, the greasy oil your skin makes to protect itself
and keep it from drying out. The sebum is produced in sebaceous glands,
which empty into the hair follicles and coat both the hair shaft and
face mite.
That's why the greasiest parts of your body, such as
around the eyes, nose and mouth, likely harbor a higher concentration
of mites than other areas.
The mites live about two weeks. They
spend most of their time tucked inside the pores, but while people
sleep, they crawl out onto the skin's surface to mate and then head back
to lay their eggs.
Since they live inside your pores, you
can't scrub them off by washing. It's basically impossible to get rid of
all of your face mites.
So how does Trautwein find and study a particular mite? With glue.
"I
actually put glue on a glass microscope slide and stick it onto a
person's forehead," she says. "Then I slowly peel it off. I look under a
microscope for mites that are stuck in the follicles that stick up from
the thin layer of skin that got peeled off."
"It can be pretty
addictive and exciting," she adds. "It's sort of a meditative process
of looking through this microforest of follicles and hairs and looking
for just the right potential movement or shape."
It seems our immune system is able to keep their numbers in check, but some people can experience problems with the mites.
"When you tell patients that they have face mites, first of all, they freak out," says
Kanade Shinkai, a dermatologist at the University of California, San Francisco.
Since face mites live inside your pores, you can't wash
them off. But for a majority of people, they're harmless.
Josh Cassidy/KQED
Shinkai occasionally treats patients who have an overload of face mites, which results in a condition called demodicosis.
"There is a very particular look to people suffering from demodicosis. We call it the
Demodex
frost," she says. "It's sort of a white sheen on the skin. And if you
look really closely, you can see [it] coming out of every pore. If you
scrape those pores, you can see it frothing with little
Demodex face mites."
The
condition is relatively rare and is often connected to a decline in the
immune system, such as receiving immunosuppressive drugs after
transplant surgery, chemotherapy or
immunodeficiency diseases such as AIDS.
Demodicosis
can also be triggered by local suppression of the immune system, like
using itch-relieving hydrocortisone cream on the face.
It
usually comes on fast. "Patients almost universally describe this
explosive development of like pustules like whiteheads on their face.
It's really dramatic," Shinkai says. "And what's really dramatic about
it is that they're often fine the day before, and then they develop it
overnight."
For the vast majority of people, though, face mites
are nothing to worry about. While some studies have found loose
connections between
Demodex and diseases like rosacea, the evidence hasn't shown a strong link.
"What's really confusing is that if you go into your office and scrape everyone's face, you would find
Demodex probably on everybody," Shinkai says. "And people who have low burden of
Demodex may have no or very severe disease and vice versa."
Trautwein also sees face mites more as a source of interest than of fear.
"They're
not dangerous in a broad sense because we all have them and most of us
seem to be cohabiting quite well with them," Trautwein says. "We mostly
share them within family units, and it seems like you are probably
initially colonized soon after birth, most likely by your mother,
traditionally speaking in human history."
Looking at your
mites, researchers such as Trautwein can usually tell something about
your geographical ancestry — what part of the world your ancestors came
from.
"Face mites are definitely the species of animal that we
have the closest connection with as humans, even though most of us don't
know about them or ever see one in our lifetime," she says. "We still
have this very ancient and intimate relationship, and it seems clear
that we've had these face mite species with us for all of our history.
So they are as old as our species, as old as
Homo sapiens."
