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:

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.


  1. luca says


    so what would be the reason for smegma to cause cancer? and how they got the idea in first place? from experimental statistical observation of human patient (circumcised and not)?

  2. craig says

    So… what percentage of the fatty acids in ear wax is omega 3?

    And why does the back of my left ear always smell like Cheetos?

  3. speedwell says

    “…why does the back of my left ear always smell like Cheetos?”

    Combination of your body chemistry, the way you react to what you put on your hair to clean it and condition it, and various microorganisms that like that area of you just swell. After your shower, clean back there with a little soap and water to remove the residue from shampoo and stuff, then dab on a little tiny bit of plain unsweetened yogurt, in case a yeast organism (that everyone has normally) overpopulated the area.

  4. speedwell says

    it’s too early for me. If that Cheetos thing was a movie quote or other sort of pop culture reference I didn’t get, I apologize, plead pre-coffee, and promise to watch more TV.

  5. Fred Gray says

    If that Cheetos thing was a movie quote or other sort of pop culture reference I didn’t get

    I got it! Hey PZ, I have a problem with over production
    of sebum. I have had severe acne for more than fifty
    years. Also have to have carbuncles on my back lanced at the doctor’s office. So I am a living cheese factory.

    By the way, if you re-chew your chewing gum that you left
    stuck to the bedpost overnight do you need to eat breakfast?

  6. CousinoMacul says

    This got me thinking about what that letter might have read like if it had been written by a creationist loon.

    “Here’s a question for you Dr. Now-it-all. Explain mucus like finger nails and ear waxs. You can’t cause the ear wax has made you blind to the truth. If finger nails evolved from fish scales, how come our bodies isn’t covered in scales like the fishes? And what are the intermidate steps that led to mucus? There are none! Answer me that! You can’t. I’m waiting for your answer.”

    (Actually I don’t know if that’s what PZ’s creationist mail is like, but I’d say about 70-80% of the one’s I’ve had the pleasure of talking to sound just like that.)

  7. says

    Im gonna guess that women mostly dont ask these questions because we spend so much of our lives cleaning up disgusting excretions – we have no need to talk about them too.

  8. says

    Ah, hell, I have no problem with the body or talking about secretions if anyone is interested in hearing about it. Why is it always the GUYS who don’t want to hear about female secretions? :)

  9. Fred Gray says

    Talking about female secretions/excretions…

    In the garden of Eden, God walked up to Adam and Eve
    right after they had eaten the apple. Adam covered himself
    with a fig leaf. Eve ran and stood in the brook up to her navel. God said “Oh no! I’ll never get that smell out of those fish.”

  10. says

    Wasn’t there some recent findings aobut the nature of earwax as a genetic marker of some sort? I recall an article about an expression of some genetic combinations in humans causing some groups to have the “traditional” lumpy, wet earwax. Other groups have evolved with dry ear wax that dries up and flakes out of their ears.

    It’s a sort of “old-world, new-world” thing (yes, I understand how bogus that term is — leave it out), with those of European descent have the former and native Americans and some Asians as have the latter.

    I continue to mis-use Q-tips by clearing out my ears regularly (any audiologist will warn you not to do this — that’s years of professional experience speaking) but now I add statements like “curse my European earwax. Curse it!” while doing it.

  11. Neutral Observer says

    Fred Gray:

    By the way, if you re-chew your chewing gum that you left
    stuck to the bedpost overnight do you need to eat breakfast?

    I presume that is a rhetorical question on the same lines as “Oy, where’s me tiger’s head”?

    As for mucus, I feel a Life of Brian quip bubbling up inside me! OK, I’ll restrain myself.

    (PS. The tiger’s head is of course “Four foot from its tail”)

  12. Neutral Observer says

    Oops, just realised, the quip would not have been Life of Brian more History of the World, Part 1

  13. says

    As an undergraduate in Biology, I was flabbergasted to find that our 3rd-year Physiology textbook did not cover lactation. Can we say, “blind spot,” kiddies?

  14. David Harmon says

    As a long-time wearer of hearing aids, I have discovered two entertaining facts about ear wax: (1) my cat likes it (2) It’s impressively flammable.

  15. craig says

    it’s too early for me. If that Cheetos thing was a movie quote or other sort of pop culture reference I didn’t get, I apologize, plead pre-coffee, and promise to watch more TV.

    No pop culture reference – the back of my left ear just always smells like Cheetos. :(

  16. Fred Gray says

    Neutral Observer said

    “I presume that is a rhetorical question on the same lines as ‘Oy, where’s me tiger’s head’?”

    See PZ’s post of Mar 20 titled “Watch out for the mudghah on the sidewalk”
    That is where the chewing gum came from.

  17. says

    “so what would be the reason for smegma to cause cancer? and how they got the idea in first place? from experimental statistical observation of human patient (circumcised and not)?”

    Actually, there has been something of an industry that has grown around circumcision in America and it is the only reason it is still practiced for ‘medical’ reasons in America which is an exception among other nations that are not largely Muslim or Jewish — in most of Europe, East Asia, Australia and the Americas with the exception if the U.S. circumcision is unheard of.

    What happened was this: Circumcision was originally prescribed in Victorian times as a cure for masturbation. After ideas about this came to be abandoned around the 30’s and 40’s doctors who made extra money in this then recommended it for cleanliness. Eventually, claims were made about circumcision reducing the risk for cervical cancer, penile cancer, probably all sexually transmitted diseases. More recently, various froms cultured skin grafts have been used as an alternative to traditional skin grafting, the culture is made from foreskins taken in circumcision. There are also skin creams that incorporate foreskin tissue. Just about all of these claims about lower risk of infection are based on very little evidence and there is no indication that anything of foreskin tissue has any benefits for the skin. So overall it seems that circumcision is largely unnecessary and perhaps even harmful considering a likelihood of accidents and possible physiological and psychological impact and that nonreligious circumcision remains purely for economic reasons.

    So, that’s the revolting story on a revolting subject in a revolting thread with another revolting subject.

  18. miko says

    Am I the only one who gets a creepy j edgar hoover vibe from this smegma research? Remember when everything was black and white and scientists wore “suits” under their “labcoats?” (OK, maybe I should still be wearing a labcoat). I picture guys like that with brill-creamed hair, puritanical fervor, and some serious hangups about sex and genitalia denouncing the smegma from everyone’s dirty filthy shameful parts, supposedly for its oncogenic (if not satanic) properties. Luckily their scientific detachment (and NOT any repressed obsession with huge mammalian genitalia) allowed them to role up the sleeves of those labcoats and collect great gobs of dead horse smegma. Honestly, they must have been funded by some agency set up to promote genital-washing as a means of preventing communism or something.

    This does give me hope to get my “cat shit causes nausea and lightheadedness” research published in Science, though.

  19. Craig Shergold says

    Sooner or later, every blog gets around to smegma.

    I recently read about a woman who was forced to “sheath” horses. Live ones. Stallions. Washing out the “sheath” with cold hose water. Some of them kicked. Some of them liked it.

  20. Neutral Observer says

    Fred Gray:

    Both chewing-gum and the tiger’s head were references to the late great Lonnie Donegan.

    Now you may have to be a Brit of a certain age to understand that.