Culturing Science – biology as relevant to us earthly beings

What’s eating you? Thoughts on Demodex, the eyelash mite

As a preface, I should mention that I am a foul creature.  I’m not really any more filthy than the rest of you scum – I shower almost every day! – but I am obsessed with my own filth.  This obsession manifests itself in different ways.  For example, I regularly take note of how much trash I create through sloth and excessive packaging, which could be beneficial in helping me reduce waste.  Mostly it makes me feel like trash myself.

But it also shows up in perhaps strange ways.  (I don’t typically think it strange, but my friends see it as an “eccentric” characteristic so maybe I am a huge weirdo.)  For example, I use pore strips not to clean my pores, but rather to look at all the gunk that was stuck up there.  “Gross! Cool! Look at all that stuff that was jammed into my face!”  I am fascinated by all the body cleanse hoaxes (despite my knowledge that they don’t work), like ear candles vacuuming out earwax, because I would love to be able to visualize my own filth.

It also has led to a complete comfort with the various invisible creatures that inhabit my body.  No, comfort is not a strong enough word: more like straight adoration.  I love my microbes!  I’m so proud of my parents for allowing me to eat so much dirt as a child!  Carl Zimmer’s NYTimes article about the fecal transplant brought me great joy (paper here), and I’ve used it to amuse at endless dinner parties.  (I go to dinner parties?)

From Warren Ellis's "Transmetropolitan" #9

And while the wild and wacky world of intestinal flora will always be cool, I often think about what is living on the outside of our bodies.  We must have some flea or mite or otherwise crawler that lives on our skin.  But how do I even find out that sort of information?  (The google search for “human parasite” doesn’t work so well.)

When I was visiting friends in New Orleans in February, a tropical diseases student, Rebecca, called me over: “OMG Hannah, come here, I have to show you something, you’re going to LOVE IT!”  (Shows a little bit about my reputation.)  She proceeded to show me pictures of Demodex spp. To say I screamed and ran in circles with joy would be an understatement.

The first Demodex specimen was collected in 1841 from a human ear canal and was initially described as a tardigrade.  (They both look pretty cuddly – you can see images here.)  It was placed in its own genus in 1843 by Richard Owen, the same guy who brought us Archaeopteryx, the word “dinosaur” and the concept of homology.  Demodex means “lard-boring worm.”  How cute!!

Demodex includes 65 species, two of which inhabit human skin: D. folliculorum and D. brevis.  The rest inhabit basically every other species of mammal: I saw literature on hedgehogs, alpacas, koalas, bears, along with the usual cats and dogs.  They bury themselves head-down into a hair follicle, with their tails sticking up, and feed on dead skin and oils built up in your pores.  That’s right, your pores.  Infants rarely have Demodex specimens, but almost all elderly people have them.  They are considered the most common human ectoparasite, and 50% of adults harbor these guys.

So on your face and in your hair you probably have a healthy population of crawly little mites!  They can aggravate disease, but it hasn’t been proven that they actually cause any dermatological disorders.  They mostly just clean up your face for you.  But it will make you think differently when you borrow a friend’s pillow, or crash on a communal couch.

It is pretty weird to think that there is an organism that evolved to live on my face, lay its eggs in my pores, feed on my filth.  Maybe I should be more careful next time I use pore strips, as to not dislodge any of my little friends.

Written by Hanner

July 27, 2010 at 7:29 am

11 Responses

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  1. That has to be the cutest thing I’ve seen in a while! Thanks, I didn’t know about them at all :))

    Skl

    August 3, 2010 at 3:55 pm

  2. I still think tardigrades are cuter :p

    Lab Rat

    August 9, 2010 at 2:23 pm

  3. “They are considered the most common human ectoparasite, and 50% of adults harbor these guys.”

    Source? That seems unlikely at least locally where I live.

    With 0.3-0.4mm size (wiki) they would be visible to the naked eye (at least to mine) and I’ve never seen them.

    Ax

    August 10, 2010 at 9:49 am

    • Well, Wiki must be wrong here – if you look at the pictures in the post, there are 3 mites feeding in one hair follicle. So definitely smaller than 0.3 mm.

      This review mentions a number of specific studies of normal population (http://dx.doi/org/10.1007/s10493-009-9272-0). This study (http://www.ncbi.nlm.nih.gov/pubmed/9646125) also found that over half the control population had these mites.

      They are described as common human skin flora and are found on humans of all races in many countries. Infestation is positively correlated with age.

      Hannah

      August 10, 2010 at 4:13 pm

  4. […] Eyelash mites: What can I say, I’m a sucker for parasitic arthropods. […]

  5. Anything that eats your filth will leave its own filth as well. I’m certain they don’t bring any benefit to anybody. Think of it this way. One or two may not cause trouble. But one or two worms in your intestines wouldn’t cause trouble either. I’d rather not have any mites on me.

    Por

    December 30, 2010 at 8:27 am

    • Actually, they don’t leave filth. They have no excretion hole. They have so little waste that they have no way to dispose it. They are completely harmless. There’s no reason to go through the trouble of getting rid of them, especially since you can easily catch them again.

      Zac

      January 5, 2011 at 4:10 pm

  6. well eyelash demodex are the most difficult to kill i had demodex mites on my face and around the eyes bu i had success treating them with Demodexin cream The eyelashes itself, it is a problem, can’t find anything to get them out of there

    Sally

    May 12, 2011 at 11:31 am

  7. I have recently moved into a house which is absolutely full of ladybugs. One lives in my bathroom and when i am in the mirror brushing my teeth etc. he flies onto my face, crawls up to my eyebrows and nibbles at the base of the hairs. Then he does the same to my eyelashes. He systematically nibbles at the base of each hair, you can really feel it. I know that ladybugs are carnivorous so I was wondering if he might be eating demodex or skin flakes or something. I will keep experimenting with this, I need to find a university or something to do some research. I reckon I’m on to something

    tom

    December 7, 2011 at 10:10 am

  8. I HATE demodex. “Zac: They are completely harmless.” Duh, no, they are not. They are very harmful. In little populations they do not cause any problems, but once their population rises they cause acne, blepharitis and more. Forgive me, but I want to see these little parasites die.

    iliketodrinkoolong

    March 9, 2012 at 6:43 pm

  9. Good day everyone! If you are suffering from human demodex specially on your lashes, you might want to read this post about my own experience regarding human demodex. On my second year in college, I had these redness and itchiness on my face specially my nose and cheeks area, including the area where the eyelashes grow. I don’t know what to do with it, I tried washing it with water but it didn’t work. So I decided to seek the help of a dermatologist, then she told me it was human demodex, I wasn’t familiar with human demodex that time so what I did is ask her about the treatment, cure or remedy for these mites. She gave me a cream for my face and lotion for my eyelashes. Their names are Cream Demodexin (made by Ovante) for the face and Eyes n Mites lotion for my eyelashes. Both products worked effectively and immediately for me, the redness and itchiness were lessened in just a few days and were totally gone in about more than a week. I hope this post would help others with human demodex. :)

    Paula Pagdanganan

    June 11, 2012 at 12:07 am


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