PZ Myers. 2005 Mar 10. That revolting article about earwax and smegma. <http://pharyngula.org/index/weblog/that_revolting_article_about_earwax_and_smegma/>. Accessed 2008 Aug 08.
Posted on M00o93H7pQ09L8X1t49cHY01Z5j4TT91fGfr on Thursday, March 10, 2005
That revolting article about earwax and smegma
Not all the email I get is from cranks and creationist loons. Sometimes I get sincere questions. In today's edition of "Ask Mr Science Guy!", Hank Fox asks,
I was thinking recently about the fact that wax collects in one's ears, and suddenly thought to be amazed that some part of the HUMAN body produces actual WAX. Weird. Like having something like honeybee cells in your ear.
And then I started to think about what sorts of other ... exudates the human exterior produces. Mucus, possibly several different types (does the nose itself produce more than one type?). Oils, possibly several different types. That something-or-other that hardens into your fingernails. Saliva, if you wanted to count our frequently-open mouth as sort-of exterior. What else?
Of course I know something about this subject, having taught physiology for a few years. My years of experience have also led me to notice that it is always the guys who ask about disgusting secretions. Why is that?
Anyway, fingernails (and hair) are not secretions. They are composed of interlocked, dead cells packed internally with high concentrations of the protein keratin. So let's forget about those, and concentrate on the really yucky stuff instead: ear wax and another important kind of goo, smegma.
First of all, it's not at all unusual that we would secrete a wax. What's the difference between an oil, a fat, and a wax? Nothing but the melting point. All are esters (the products of condensation reactions between carboxylic acids and alcohols) with an aliphatic chain of carbon molecules. The length of the chain determines the volatility of the molecule; short chains are more fluid, long chains more solid. Something like olive oil will have shorter chains than something like beeswax, but all are fundamentally similar. They are all classified as lipids.
So earwax isn't that unusual—it's a compound on a continuum of perfectly normal lipid products produced by cells.
So what, exactly, is in earwax, or cerumen? Here's where it gets ugly. It's a combination of things:
- Desquamated keratinocytes. Dead skin cells, in other words, that have peeled off of the epithelia lining the ear canal.
- Sebum. This is an oily substance produced by the sebaceous glands that are scattered over most of your body. If you don't wash your hair for a few days, you know that oily, greasy substance that builds up? That's sebum.
- Various waxes. The dense, waxy part of cerumen is a secretion from specialized glands in the ear canal, the ceruminous glands.
All of these combine into a greasy paste that helps protect the passageway into the ear from invaders. I know I wouldn't want to set foot in it.
For a more detailed analysis of the chemical composition of ear wax, one can do a little chromatography. About half of the dry weight of ear wax is lipid, and it consists of:
- Cholesterol and cholesterol esters: 32.5%
- Fatty acids: 22.7%
- Ceramides: 18.6%
- Squalene: 6.4%
- Triacylglycerols: 3.0%
Everyone with a little biology or chemistry background will recognize these as quite ordinary products of cellular metabolism. Also, these particular compounds are found in similar concentrations in another place: the stratum corneum, or outer layer, of your skin, where the fats and waxes and oils are secreted in a layer that surrounds the cells, providing waterproofing and lubrication.
While rummaging around in the files, I also found an older paper (from 1947) that analyzes another similar substance: smegma. As you might expect from the fact that it is also a waxy, oily secretion from skin cells, it is also about half lipid, and consists of:
- Cholesterol and cholesterol esters: 18%
- Fatty acids: 71%
This paper is notable for a couple of things. It tells us where to get a supply of smegma.
Smegma is best obtained from dead horses in rendering plants or from anesthetized animals in a department of veterinary surgery.
That's good to know; I wouldn't want to make the error of trying to collect smegma from live, conscious horses.
The other distinctive thing about the paper is that it is one of the more disgusting experiments I've read about. The authors were testing the potential carcinogenic effects of smegma, and the experiment involved making up slurries of smegma and smearing it or injecting it into folds of skin on mice, and assessing their health. It had to have been a big job, slathering 400 mice with smegma every week, and treating another 400 control mice with ear wax.
This study found an increased frequency of various cancers in the treated mice: 57 smegma-smeared mice developed various kinds of cancer, versus only 12 of the controls. Before everyone gets all worked up into the circumcision debate, though, I'll mention that the paper is one of many that have tested this kind of thing, they acknowledge that other researchers have seen no carcinogenic effect, and that more modern papers suggest that there are no special carcinogenic properties of smegma. The paper shows another curious result, that the authors didn't even discuss:
There was no significant difference in the survival rates of treated and control mice up to the 400th day of life: 85 and 88 per cent, respectively, after 200 days; 74 and 80 percent after 300 days; 65 and 57 percent after 400 days. After 500 days, 47 percent of those treated with smegma were alive as compared with 30 percent of the controls. From the 600th day on, there was a marked difference (26 and 6 percent, respectively), and on the 700th day, the survival rates were 12 and 1½ per cent.
Personally, I think the smegmated mice were just so pissed off that they kept going out of infuriated spite.
By the way, Hank also asked about mucus, but I think I'll save the discussion about snot for another day. Right now, it's time for me to go to lunch.
Bortz JT, Wertz PW, Downing DT (1990) Composition of cerumen lipids. J Am Acad Dermatol 23(5):845-9.
Plaut A, Kohn-Speyer AC (1947) The carcinogenic action of smegma. Science 105(2728):391-392.
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Thank you for the laugh! Informative too!
#: Posted by Sean D. Hurley on 03/10 at 11:58 AM
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Some hotshot scientist recently said that smegma was partially responsible for the survival of the human race (maybe all animals with penises? I forget...). I don't claim to know enough about it to comment, but it sort of through me for a loop. Hell, I've never had smegma: I'm cut and shower daily. Technological culture in some ways removes the need for nature's solutions, dunnit?
#: Posted by Heliologue on 03/10 at 12:04 PM
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PZ, I learn the most interesting things each morning reading your blog.
Over breakfast.
With milky cereal.
Or cheesy eggs.
Things I'm not even sure I'm supposed to know. -
Thanks! Now, when conversation lags and one of those uncomfortable pauses comes along, I can pipe up and say "Hey, I bet you guys didn't know that researchers get their supplies of smegma from dead or anesthetized horses, did you??"
But then I'd have to explain to many what smegma was, alas.#: Posted by Janice in GA on 03/10 at 12:23 PM - I can't help but imagine Michael Palin as the junior assistant researcher sent to the slaughterhouse to collect the daily, um, stuff, and attempting to explain to John Cleese what he was there to get, and why.
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Once upon a time I played bass in a garage
band called Smegma and the Four Skins.#: Posted by on 03/10 at 01:09 PM -
"All of these combine into a greasy paste that helps protect the passageway into the ear from invaders."
Does this mean I should keep it in? That it's essential to my body's defenses? I don't think Mom would like to hear that...#: Posted by on 03/10 at 01:34 PM -
Wonderfully informative. Now perhaps a study could be done on those people who eat their earwax, and why such a behavior has been maintained in an evolving species.
#: Posted by Rexroth's Daughter on 03/10 at 02:03 PM
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Thought I better comment, what with my chosen handle and all.
All I can add though, is: Fascinating.#: Posted by on 03/10 at 02:18 PM -
The only think more gross than reading the original article about the gunk is reading the comments.
#: Posted by on 03/10 at 02:29 PM
- Gosh, I'm so glad I read that.
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Dear Mr. Science Guy, et al.,
I know that biodiesel can be produced from a variety of lipids through a fairly simple process of transesterification. Since I just purchased a diesel-powered car, this process is of great personal interest, and I would like to know if I can make a usable fuel or fuel additive from my own earwax.
Assuming that I can efficiently remove the dead cells from the earwax, do you think the transesterified aural lipids would be short enough to burn efficiently in an unmodified engine? Would I get better mileage if I mixed the ear wax with nasal mucous and/or vaginal secretions before processing? I would rather not add smegma (the high percentage of free fatty acids would likely have adverse effects on the reaction kinematics, and I'm not sure that my boyfriend really appreciates the environmental importance of human-derived biofuels) but if you think it might have a beneficial long-term impact on my engine I would be willing to try. Please advise. -
Just how much earwax do you produce? Do you wear earrings that bear a striking resemblance to large buckets?
In that paper that used earwax as a control in their tests of smegma carcinogenicity, they neglected to mention their source for that. Were your grandparents, by any chance, involved in biomedical research in the 1940s? - Methods for increasing the production of earwax were deliberately left as an exercise for the questioner ;)
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Hey, girls like spooge, too. The allegedly carcinogenic properties of smegma made for delightful reading over my late afternoon snack. I'm looking forward to your scientific treatise about snot.
#: Posted by Trish Wilson on 03/10 at 04:04 PM
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So, what causes a softer or more liquid ear wax? I presume the carbon chain length wouldn't change, so a different ratio of the components could be a cause. Or could there be more water content - this would assume that the wax will mix (emulsify) with water.
#: Posted by on 03/10 at 06:02 PM
- Since it's a mixture of sebum and the output of the ceruminous glands, variations in the relative amounts of oily vs. waxy will change the consistency.
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Was it Rox Populi or some other blog where you get banned if you use the word "smegma"?
Anyway, now I have to add this PZ post to my last night's "Penis blogging week" post.... - ...another association: on big horse stud farms, stallions penises need to be washed on a regular basis and it is traditionally done by female staff as the belief is that their "female touch" is going to prevent them from getting killed. Is this just a European thing?
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Naah, it's just that the guys didn't want to be seen handling another male's penis.
Way interesting, PZ, WAY interesting..
Sravana#: Posted by on 03/10 at 09:06 PM -
As for the stud farms, staff, and gender bias in washing of equine copulatory organ (oh, if we must, then we must: PENIS) responsibilities: not sure. I'd wager that generally there are more females that work on horse farms, breeding farms or otherwise. I was under the impression that equine penis-washing establishments were equal opportunity employers. I've been in a few breeding sheds, and I don't even remember who handled the horses, so I don't think a disparate gender bias struck me.
Besides, wouldn't you think that the *male* staff would be more ... educated ... in penis-washing-handling duties? Or is this seemingly low percentage of male equine penis-washers due to penile intimidation?
By the way, the mare gets a wipe-up, too. Does this mean that male staff tend to her, and let the ladies wash the stallion?#: Posted by on 03/10 at 09:09 PM -
Colestrum, lochia, and meconium are good conversation stoppers at baby showers.
#: Posted by John Emerson on 03/10 at 09:22 PM
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I am posting this anonymously as people I know read this blog.
I have often thought about ther stuff we humans secrete, and there's one I wonder about - WARNING GROSS STUFF AHEAD
Ok, there's this stuff that comes out of the anus, it is clear with perhaps a very slight white/yellowish color... and it is extremely slippery. So slippery that I have figured that its some sort of natural lubricant.
I have read that people with IBS sometimes have a secretion that sounds like what Im talking about instead of feces when their stomach is churning. I have IBS so who knows.#: Posted by on 03/10 at 10:04 PM -
When I was playing the part of Receiver during some home birth sessions awhile back, I noticed a particular grease, grey/white, that coated the bodies of the newborns. When I asked about this later, someone used the word "vernix" on me. Is this similar to smegma? I remembered thinking that it should, maybe, be rubbed into the baby (but it was a wet climate, and I had occasion to grease my boots regularly). Is this what ungulates are licking from the skin of their offspring? I didn't taste it, I don't think... ^..^
#: Posted by on 03/10 at 10:33 PM
- Well, vernix is a cheesy, oily goop secreted by the sebaceous glands, so I suppose it is very similar...but I don't recommend telling mothers that their newborn is covered with smegma.
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Fascinating! Civilization makes us to clean and wash all oleous liquids we naturally produce, such as skin oils, and to replace them by artificial perfumed cremes and oils. Ear vax cleaning is an industry, specialized instrument sold everywhere. Is there a market for artificial ear wax for artificial perfumed smegma-like lubricants for us circumcized smegma-less males? Also, naturally produced mucus must be beneficial for something, artificial one must be even better. Yellow-greenish is so sickly, orange would be nicer.
#: Posted by on 03/10 at 11:48 PM
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Years ago I read a novel in which an ear-nose-and-throat doctor took the ear wax he removed from his patients and, as a hobby, made candles of it.
Is this possible?#: Posted by on 03/11 at 12:33 AM -
Ewww, so basically earwax = blackheads?
I have pointed the person in my household, who has a nasty habit of tasting their own earwax, at this article. I hope never, ever to have to see that behaviour again after he reads it.#: Posted by Republic of Palau on 03/11 at 04:02 AM - Now I remember why I went from the sciences over to the humanities. ugh....
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Xboy,
was that something by Pynchon by any chance?
As for whether earwax candles are feasible -- this is a science blog! There's only one way to find out. Be sure to write up your results -- sounds like a shoe-in for Nature.#: Posted by Mrs Tilton on 03/11 at 05:20 AM -
And for hints on experimental methodology, see "Shrek". Because, as we all know, Hollywood always gets science right.
#: Posted by Republic of Palau on 03/11 at 05:53 AM
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Palau, earwax is harmless. Maybe too much cholesterol?
BTW, I always noticed that chimps in zoos love to sniff and taste their own smegma. I think the subject is still virgin to research.#: Posted by on 03/11 at 06:34 AM -
so did breast milk evolve from one of these fatty cheesy incidental secretions?
#: Posted by on 03/11 at 07:10 AM
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Sweet! More grist for the dinner table; my wife will make that face and my daughters will laugh. Better living through biology.
#: Posted by on 03/11 at 08:47 AM
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thanks for the earwax stuff. I recently had ear surgery that was somewhat invasive (outer ear partially detached and pushed to the side, to allow better access to the creamy inside, then things removed (growth of excess skin into middle and inner ear -- aka cholesteotoma) or replaced (ear bone (dissolved by aforementioned cholesteotoma) with titanium widget, ear drum with some tissue made available by the initial invasion). Anyway, part of the recovery process seems to entail incessant secretion of ear wax and other quasi-liquids, especially while prone at night, so anything about earwax is an eyecatcher for me just now.
#: Posted by on 03/11 at 10:27 AM
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I have one bone to pick with you, and it's minor, but important. Loons are perfectly wonderful birds who do not adhere to a creationist agenda any more than does any other bird. I am sure that you have offended all good loons everywhere, despite the fact that their populations are declining, due to habitat loss, among other things. It'll be a sad day when loons go the way of the Dodo.
#: Posted by GrrlScientist (Hedwig the Owl) on 03/11 at 12:42 PM
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See what you have wrought, PZ?
I beginning to think y'all got spring fever. -
Can I get a complete citation for the smeg article?
#: Posted by on 03/11 at 06:52 PM
- Whoops...I put it out before I'd patched that in. I've fixed it now.
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Okay, the breast milk question has me intrigued now.
Regarding the creationist question "Of what use is half an eye?" the best answer I've heard cited the range of eyes that exist in animals today, from the simple eye spots of flatworms to the most complex "complete" eyes with variable-focus lenses, irises, etc. -- all undeniably useful to the organisms which characteristically sport them.
The argument showed how complex eyes probably evolved, by demonstrating a progression of usefulness in parallel with small steps in complexity.
So, PZ: Of what use is half a tit?
Do there exist in nature today a range of ... sustenance delivery systems ... that fall short of the modern mammalian teat-and-milk model, but that perhaps serve to illustrate a reasonable evolutionary pathway to breast-feeding?
But maybe that's a question for another thread.
And, oh yeah, don't forget about the snot lecture. <grin> - Platypus has milk glands but no nipples. The secretion just flows down the hair and the pups lick it.
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Pigeons, penguins, and flamingos all have special glands which secrete a kind of milk. (This is different than regurgitating half-digested food, which many birds do.) These three species aren't closely related at all, so it must have been independent origination. I don't know anything about the kind of milk produed or how it's produced, compared to mammalian milk.
#: Posted by John Emerson on 03/12 at 10:17 AM
- I've got to put the search function back in place here. I wrote about Mother's Milk some time ago.
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The novel was The Dick Gibson Show by Stanley Elkin. All about a late-night radio talk-show host and his oddball guests.
#: Posted by on 03/15 at 11:01 AM
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Two other experiments spring to mind that might just top the smegma one. The first was the isolation of elemental P after concentrating gallons and gallons of soldiers' urine (1669, Brandt). The other was the isolation of < 1 mg of testosterone from several tons of homogenized bull testiscles! (1930's.
#: Posted by on 03/15 at 01:24 PM
- Ha! I want to know who coughed up the funding for the 'covering mice with smegma' project. How do you go about proposing that?
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Oh, the horse details. Well, there are stallions (with testicles) and geldings (without).
Yes, breeding stallions do have their penises washed before "live cover" -- breeding a mare -- or semen collection, for sanitary reasons unrelated to smegma. In the case of live cover, it is because the herd isn't closed -- there is the opportunity to pass infections from one mare to the next via the stallion. If the semen is being collected (that is, the stallion ejaculates into a device rather than into a live mare) it is to reduce the chance of introducing bacteria into the semen.
Geldings tend to develop a buildup of smegma because their penises don't become erect as often as stallions, so the mechanically, the material isn't dislodged. It isn't strictly speaking necessary to clean it, but the smegma buildup can cause an offensive odor and a sticky deposit on the inside of the horse's thighs. It can also build up on the inside of the urethra, partially blocking the flow of urine.
Most horses do not need anesthesia for the penis-washing operation. The stallions can't be sedated as it would interfere with erection and ejaculation. Good stallion management is training the animal to a routine, so the washing operation is just part of the prep process. Most geldings can also be conditioned allow penis-handling without a fuss. However, for the geldings, sedation is not uncommon, as many of the sedating drugs have the side effect of relaxing the muscles which hold the penis in the sheath, so it drops down, which makes the washing (or smegma harvesting) procedure easier and more efficient.
And the women's touch? There is an incredible amount of old wives' tales in the equestrian world -- and horsefolks anthropomorphize to an astonishing degree.