Everything you never wanted to know about the mites that eat, crawl, and have sex on your face

By Ed Yong | August 31, 2012 8:59 am

New Scientist published a story yesterday stating that rosacea – a common skin disease characterised by red blotches on one’s face – may be “caused” (more on this later) by “tiny bugs closely related to spiders living in the pores of your face.” Tiny bugs that “crawl about your face in the dark”, lay eggs in your pores, and release a burst of faeces when they die.

This is the terrifying world of the Demodex mite. And by “terrifying world”, I mean your face. For anyone who wants to know more, and who isn’t currently clawing at their cheeks or bleaching their head (health tip: don’t), here’s everything you never wanted to know about your face-mites.


Say hello to my little friend

Mites are relatives of ticks, spiders, scorpions and other arachnids. Over 48,000 species have been described. Around 65 of them belong to the genus Demodex, and two of those live on your face. There’s D.folliculorum, the round-bottomed, bigger one (top image, above) and there’s D.brevis, the pointy-bottomed, smaller one (bottom image, above). These two species are evolution’s special gift to you. They live on humans and humans alone. Other Demodex mites have similarly specific preferences: D.canis, for example, is a dog-lover.

Both species are sausage-shaped, with eight stubby legs clustered in their front third. At a third of a millimetre long, D.folliculorum is the bigger of the two. It was discovered independently in 1841 by two scientists, but only properly described a year later by Gustav Simon, a German dermatologist. He was looking at acne spots under a microscope when he noticed a “worm-like object” with a head and legs. Possibly an animal? He extracted it, pressed it between two slides, and saw that it moved. Definitely an animal. A year later, Richard Owen gave the mite its name, from the Greek words ‘demo’, meaning lard, and ‘dex’, meaning boring worm. The worm that bores into fat. I can only assume that Simon and Owen spent the rest of their lives feeling a little itchy.

These mites are our most common ectoparasites (those that stay on the surface of our bodies, rather than burrowing inside). They’ve been found in every ethnic group where people have cared to look, from white Europeans to Australian aborigines to Devon Island Eskimos. 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!)”

But it’s hard to say exactly how common they are. The first estimate came from a 1903 study, which found the critters in 49 out of 100 French cadavers. The next count, from 1908, found them in 97 out of 100 German cadavers. The nationalities are probably a red herring. What’s clearer is that age matters. The mites aren’t inherited at birth, so each generation picks them up anew, probably from direct contact with our parents. Thanks, parents! If you’re under 20, good news! A French study from 1972 says that you’ve only got a 4 percent chance of carrying Demodex. If you’re old, bad news! You’ve almost certainly got Demodex somewhere.

The mites spend most of their time buried head-down in our hair follicles – the stocking-shaped organs that enclose and produce our hairs. They’re most commonly found in our eyelids, nose, cheeks, forehead and chin. That’s not to say they’re restricted to the face: Demodex has been found in the hairs of the ear canal, nipple, groin, chest, forearm, penis, and butt too. Generally, dry skin is a turn-off for them. They prize bodily real estate that’s flooded with oils (sebum). This explains why they love your face. It might also explain why their numbers are apparently higher in the summer, when hot temperatures ramp up sebum production.

A mite-y existence

How do Demodex mites spend their time? They eat! Some say they eat sebum, but Nutting thought that such a diet wouldn’t be nutritious enough. Instead, he said that they feast on the cells that line the follicle, sucking out their innards with a retractable needle in the middle of a round mouth. On either side of the mouth, D.folliculorum has a seven-clawed organ (a “palpus”) for securing itself to what it’s eating. “All of the structures formed a sharp, offensive weapon,” writes Xu Jing, who first looked at them under an electron microscope. (D.brevis, with its five-clawed palpus, was branded as “less offensive”.)

They crawl! They move about in darkness and freeze in bright lights. The fact that mites have been found on the surface of the skin suggests that they emerge from follicles at night for shadowy strolls across our faces. With their stumpy legs, they’re hardly fast. It would take almost half a day for Demodex to cover the distance from your ear to your nose.*

They don’t poo! The mite has no anus, and stores its waste in large cells within its gut. Nutting saw these as adaptations for a life spent head-down in a tightly closed space. When the mite dies, its body disintegrates and the waste is released. More on this later.

And they have sex! On your face! Their favourite hook-up spots are the rims of your hair follicles. Males outnumber females by three to five times, but this detail aside, Demodex sex lacks much of the horror found throughout the arachnid clan. No traumatic insemination. No cannibalism. The penis and vulva are hidden within the pairs of legs. (Jing wrote that D.folliculorum’s penis “looks like a small candle when it was elongated”. He failed to see D.brevis’s.)

After sex, the female buries into the follicle (if it’s D.folliculorum), or into a nearby sebaceous gland (if it’s D.brevis). Half a day later, she lays her eggs. Two and a half days later, they hatch. The young mites take six days to reach adulthood, and they live for around five more. Their entire lives play out over the course of two weeks.

People with rosacea should look away now

Are they parasites, or something more benign? For the most part, it seems that they eat, crawl and mate on your face without harmful effects. They could help us by eating bacteria or other microbes in the follicles, although there’s little evidence for this. Their eggs, clawed legs, spiny mouthparts, and salivary enzymes could all provoke an immune response, but this generally doesn’t seem to happen.

But like many of our body’s microscopic residents, Demodex appears to be an opportunist, whose populations bloom to detrimental numbers when our defences are down. Several studies, for example, have found that they’re more common in people with HIV, children with leukaemia, or patients on immunosuppressive drugs. Perhaps changes to the environment of the skin also allow the mites to proliferate beyond their usual levels.

In dogs, an overabundance of D.canis can trigger a potentially lethal condition called demodectic mange, or demodicosis. In humans, these blooms have been linked to skin diseases like acne, rosacea and blepharitis (eyelid inflammation). The New Scientist piece will undoubtedly bring this to many people’s attention, but scientists have been talking about such connections for decades. The rosacea link was first put forward in 1925!

Dermatologists have since repeatedly found that Demodex is more common in the cheeks of people with rosacea. In one study, those with the condition had an average of 12.8 mites per square centimetre of skin, compared to 0.7 in unaffected people. And according to an analysis of 48 separate studies, people with rosacea are eight times more likely to have a Demodex infestation. Obviously, correlation not causation, blah blah blah, you know the drill.

There’s plenty of anecdotal evidence about mite-killing treatments and clinical improvements (here’s the latest involving tea-tree oil), but very little in the way of hard clinical trial evidence. An example: metronidazole is sometimes used to treat Demodex infestations, and there’s evidence from three clinical trials that it’s effective at treating rosacea (a Cochrane review, and everything!). Then again, Demodex can survive high concentrations of metronidazole, so maybe the mites are irrelevant to the substance’s actions.

In the new review, covered by New Scientist, Kevin Kavanagh suggests that rosacea may be caused not by the mites themselves, but by the bacteria in their faeces. After all, antibiotics that kill the bacteria, but are harmless to the mites, can sometimes successfully treat rosacea. But again: more correlations. The bacterial angle is fascinating, though. We know so little about these creatures that colonise our bodies, and now we must contend with our even greater ignorance of the creatures that colonise their bodies. Down the rabbit-hole we go!

And finally, if all of this sounds unbearably revolting, spare a thought for people with acarophobia – the fear of mites and other “small bugs that cause itching.” What words of solace can we offer to them? Here’s Nutting:

“Those patients with acarophobia (approximately 12 have been seen in our laboratory) seem curable if they follow a prescription which includes a relaxing vacation at the beach. If they insist on a follow-up examination for hair follicle mites, the situation is a bit delicate because most will still be positive. Diplomacy will prevail—only two of our 12 have failed to respond!”

Images: top photos from Nutting, 1976, HAIR FOLLICLE MITES (ACARI: DEMODICIDAE) OF MAN.

* One review I read quoted their speed at 16 centimetres per hour. Another said 16 millimetres. Given the stubby legs, the centimetre value surely cannot be right, so I’m going with millimetres.


Comments (41)

  1. I love everything about this post. Even if my face now feels itchy.

  2. Awesome post, Ed! Our group has been talking a lot about mites lately – in fact, we have an intern working hard to find them (she’s sampled a lot of faces) and has had a hard time finding them. Maybe she needs to start looking at older folks, as you suggest?

  3. Anthony

    I’d feel a little better about it if I knew they were doing some sort of good and not just mooching (munching?) off me waiting for my immune system to weaken.

  4. Too bad there is no “like” button. Although, people would be frantically pushing it! Everything you write is interesting but putting together such a thorough post in such a short time..

  5. jonw

    Long ago I read a poem about the rabbit-hole succession of ever-smaller parasites on parasites. I wish I could remember it. It included the rhyming words “bite em” and “ad infinitum”…

  6. On Poetry, by Jonathan Swift. http://www.online-literature.com/swift/3515/

    So, naturalists observe, a flea
    Has smaller fleas that on him prey;
    And these have smaller still to bite ’em,
    And so proceed ad infinitum.

  7. Tabitha

    I’ve been wondering a lot lately about a possible link between yeast and rosacea … as a sufferer, I am in a unique position to “experiment” on myself. I particularly thought it was interesting, then, that you mentioned the link between the mites and immune system function, as well.

    Thanks, even though I am little grossed out now :)

  8. As I mentioned elsewhere, we’ve got a feature on demodex coming out next week, which meant several weeks of proofing and editing in the office.

    …at the end of it all, we each had tea tree oil wipes on our desks. Just, you know. Because. It’s so hot out! They feel good! KILL THE MITES!

  9. Really good read – thanks, Ed! Now excuse me while I scratch my face for 10 minutes…

  10. rbrtsnts

    Couldn’t you just sleep with the light on for a while… How long would they take to starve?

  11. Wei

    Impressed how you slipped in a Scarface quote.

  12. Charlie MacLeod

    The human biome…..ain’t it grand?

  13. Ratilda

    They are well-known in Europe and people who turn to a dermatologist asking for advice about their acne are usually sent to a lab to undergo a simple test for Demodex. Then, if any mites are found, the doctor suggest to make sure that you have at least 8 hours of sleep each day, to reduce your stress levels, and prescribes an ointment that has Benzoil Benzoate as an active ingredient. Tea tree oil and birch tar soaps help too.

  14. So, they look scary, poo on our face, have sex on our face, and they might cause all sorts of skin conditions. I have rosacea, why don’t they explain how to kill these things. Tea tree oil should do the trick but it is too harsh on rosacea skin, what else is there?

  15. Mister Groucho

    Any recommendations? Or is washing with soap and water a good “antidote.”?

  16. Barry OConnor

    As “parasites” go, Demodex are pretty inocuous. So much so that unless you tell people about them, they’re oblivious! At least we are spared the Demodex species that inhabit the Meibomian glands (on underside of eyelids for lubricating the eyeball) like many other mammals have!

  17. Torbjörn Larsson, OM

    A mite hard to face…

  18. matteblack

    I began itching almost 7.5 years ago, mostly on the crown of my head and forearms. The itchy bumps (like the worst, most epic mosquito bites you can imagine) spread to include my entire head, back and chest. I have since been treated for every condition imaginable: allergies, acne, MRSA and of course, rosacea. I have spent thousands on various types of antibiotics and medications, both prescription and OTC. One pleasant but ultimately uncurious Dermatologist told me that, after three years, “I’ve done everything I can” and assured me that rosacea is a chronic condition and that there is no cure, only maintenance.

    I don’t remember the actual moment I first heard about Demodex and I think it probably started to filter through on some of the rosacea forums. The descriptions of Demodex infestation matched the pathology of my ailment so exactly that I almost cried. And if anyone thinks that this is a minor or livable condition, it is not. It had me considering suicide on two very brief occasions and that was scary indeed. Amateur treatment options abounded on the internet and I have found two that seem to work. The first is a daily scrub (hard scrubbing with a washcloth) with a mint and tea tree oil shampoo from Organix. This ordinary shampoo has had a more profound effect than any of the prescription meds I have ever tried. The second was a treatment with Permethrin that I talked my GP into and which almost wiped it out completely, almost. My GP was unwilling to go further and referred me to a Dermatologist which was an immediate dead end diagnosis of rosacea and more ineffective Oracea antibiotic. I have since moved on to the Ivermectin underground. Ivermectin is the drug that is used to successfully treat river blindness and other conditions involving arthropods. I now occasionally use a veterinary form that is used intravenously on cows and which helps to keep the condition controlled. I believe Galderma is working on cream that contains Ivermectin as its active ingredient for the control of rosacea.

    I believe that the dermatologic community has really failed to recognize the strong evidence that at least some rosacea is caused by Demodex and that they continue to waste millions on completely ineffective measures when a simple, well tolerated test with Permethrin and/or Ivermectin would probably stop a lot of suffering.

  19. Lynda

    So if they don’t poo, how do you get feces that may cause rosacea? Which is it?

  20. matteblack

    I should probably have included in the above post that I use the veterinary Ivermectin TOPICALLY and do not inject it, that would be really crazy and I’m not there, yet.

  21. Frenk

    Great post, but… Xu Jing’s surname is Xu, not Jing (as referred to in the post). The practice in China (Xu Jing being a distinctly Chinese name), Japan, Korea, and so on is to place the surname first. This lack of basic cultural competence is common in the West but we still have time to learn before the alien overlords arrive and make us realize we’re all brothers and sisters…

  22. markus

    a good read…

    i wonder if any other living thing eats them?

    i’m sorry to hear about your story matteblack i wish you the best of luck and i hope that you never think about suicide again.

    people do care.

  23. Steve

    Can I Train Mine To Do Tricks ??

  24. KN

    Has anyone tried turmeric?

  25. ZL 'Kai' Burington

    One of my “if I ever got time” projects to is inferring the phylogeny of Demoxdex mites and comparing this to the host phylogeny, the mammal phylogeny. I suspect there is some congruence of evolutionary relationships, as the Demodex mites likely diversified with the mammal lineages, but I also suspect some host jumping from interspecific interactions. Very interesting stuff.

  26. Dave

    Good overview. The only thing missing is the place of follicle mites in literature – which I believe is completely subsumed into Jay Hosler’s Sandwalk Adventures wherein Darwin and a follicle mite in his left eyebrow have an extended discussion on gods, myths, and natural selection.

  27. molybrea

    I want that on a T-shirt:

    Eye Mite

  28. Oh, Barry. We can talk about eye mites and parasites, if you like. I have a whole book. Literally.

  29. ophu

    Good to know about the tea tree oil. I use it to shave.

  30. Haymoon

    @jonw & @ED Yong

    The verse I heard goes like this

    “Great fleas have little fleas upon their backs to bite ’em,
    And these fleas have lesser fleas, and so ad infinitum.

    attributed to Victorian era mathematician Augustus De Morgan

  31. Kev

    I now reckon I might have a shave tomorrow, and then bathe in tea tree oil, for an hour, just to make sure.

  32. Katkinkate

    What about alcohol or methylated spirits? When I did animal collecting (invertebrates only) for a uni course we used ethanol to quickly kill and preserve our samples in the field. Could a quick ethanol, isopropanol or metho wipe kill off enough to prevent the problems that seem to come from overgrowth of the population?

  33. Giligain

    The older you get, more likely to have mites? Is this why Grandpa smelled like, well, grandpa?

  34. A fascinating and revolting article. Yes, it made me feel itchy! It is very interesting to think that there may be some common skin conditions (or other illnesses) that may be treatable if these little creatures are carefully examined and understood. Perhaps like curing stomach ulcers by treating bacterial imbalance. Who knows?

  35. very interesting — great encouragement for me to stop applying ointment to those red blotches on my nose, and “scrub” with a washcloth and apply tea tree oil.
    Since I can’t see my own face except in a mirror I can only guess what dreadful sight my nose must present coming at you, red spots in the fore.
    Doesn’t bother me as I forget about me, neither does this article. So what? – all sorts of microscopic “things” must be going on outside and inside one’s body. It doesn’t itch on me. I’m sorry to hear about other people’s misery with this condition.

  36. …Both species are sausage-shaped, with eight stubby legs clustered in their front third. At a third of a millimetre long, D.folliculorum is the bigger of the two…

    Is that 1/3 mm length correct? Seems a tad large – enough to see with naked eye…and we cant have that!

    Great article, thanks.

  37. I have never seen a bug or anything crawling in my bed or on my body or hair
    How do you know you have these things? My hair and skin is healthy and I never had any redness or any marks on my face or body

  38. Susan Courtnay

    Oh WOW! I love gross human physiology stuff! I will definitely be talking to my high school science students about this. I have recently started to suffer from itchy, stinging eyes in the morning with a little crust along the eyelash area. Since I am going to be officially “old” in a couple of days (60) maybe I now have enough mites to cause me a problem. Think I’ll invest in some tea tree oil and see if it helps. I absolutely feel little microscopic feet marching cross the vast plains of my face, even sitting here in the daylight….have they adapted already??!! ARGGG..

  39. Renee

    Thank you for spreading the word on this horrible secret problem. I have had it for a year now and determatologists don’t help. Tea tree helps a little, but I can’t find anything to kill them. It is very upsetting to see the trail of bites on my face EVERY day and know that these tiny monsters are winning the battle. Please someone find a way to get rid of them once and for all!

  40. R. J. Redfield

    Just an anecdote…

    I’ve been getting itchy red bumps on my face for years; now I think each might be caused by a mite dying and releasing its allergenic bacteria. The tea tree oil paper I read (http://bjo.bmj.com/content/89/11/1468.short) said it drove them from their happy homes. That sounded good – I don’t want to kill them in the pores and release their bacteria, I just want them to go away.

    So I’ve been wiping my face with tea tree oil every few days for the past month or so, washing it off after about 10 minutes. No more itchy red bumps!

  41. Eileen

    What a great read, my whole life I had basically clear skin on my face. The past year I went from clear as day to red clusters,bumps and pustules starting on my chin and slowly now up to my cheeks. My dermatologist has treated me for so many different things from fungal to skin infections. I have used so many creams. I finally had a biopsy last week and the results show and “over infestation” of these guys. I am not sure what it is she is ordering for me, but I will start treatment in a day or so. I am really excited to have an answer. My faces has felt (and looks) like I have poison ivy constantly. It is borderline unbearable for me.


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