Friday Weird Science: Smells Fishy? Check your semen.

Apr 16 2010 Published by under Friday Weird Science

Sometimes, Sci is simply inundated with weird science opportunities, and such a week is this one. There is SO MUCH WEIRD OUT THERE, you guys. This is great, as it keeps Friday Weird Science in business, but sometimes Sci has to file away so many for later that she loses track. Here's really hoping that she WON'T lose track, because she found some real beauties today. And this was one of the best one.
In response to a question from awesome reader and friend of the blog Pascale: Can I post on semen analysis and the importance of odor?
Oh yes, yes I can.
ResearchBlogging.org Chvapil, et al. "Studies on vaginal malodor: humans". Obstetrics and Gynecology, 1978.
Time for some historical, weird, and seminal (mwah ha ha ha) science!


The best part of this paper may actually be its opening sentence. It has the ring of truth and humor resonant of only the great works, and it calls to Sci's mind the open line from Jane Austen's Pride and Predjudice: "It is a truth universally acknowledged that a single man, in possession of a large fortune, must be in want of a wife."
This one does Jane one better: "The available studies analyzing vaginal odors have been concerned mostly with sex-attractant properties of volatile aliphatic acids of vaginal secretions." Pure poetry. Ok, maybe it's just me.
Anyway, contrary to the many immature and annoying things you'll hear about "pink taco stands" and "fish", it turns out that most people find vaginal odor (obviously clean vaginal odor) fairly attractive, though this varies somewhat over the course of the menstrual cycle. But not all women have "attractive" smelling odors, whether due to hygiene, bacterial or fungal infections, or...sexual activity.
This whole study arose from a study of contraceptive sponges. They aren't as popular as they once were (back in the 70's when this study was done), but contraceptive sponges are a pretty effective form of birth control (when used properly, around 91% effective, which is close to what you'd get with a condom, but of course there's no protection from STDs). Basically, it's a little sponge that a woman puts up her vagina against the cervix right before sex. The sponge is filled with spermacide and gets the little buggers before they have a chance to get anywhere.

But women started noticing something. Advertisements said that you could keep the sponge in and reuse it. Apparently women took that literally (I believe you were supposed to wash and THEN reinsert, but apparently that's not the impression these women got), and after about five days, 1/3 of the users reported a distinct, and HIGHLY unattractive vaginal odor.
This study set out to figure out why. They gave the sponge to a group of women, some sexually active, some not, and checked for odor in the sponge under a variety of conditions. Pascale and I both had cause to wonder what poor grad student got THAT job.
The conditions tested included the acidity of the sponge (between a neutral pH of 7.0 and an acidic pH of 3.5), the effect of sexual activity, the retention (and whether washing helped), and what chemicals were present in the sponges with and without odor.
They found several interesting things:
1) Sexually active people kept the sponge in for LESS time than sexually inactive people (5 vs 12 days). But sexually active people had FAR more smells (34% vs 4%)
2) The pH of the sponge didn't seem to effect how fast odor formed, but the mid range pH of 5.5 is considered best.
3) Taking out the sponge within 24 hours of sexual intercourse and washing it (in vinegar to keep the acidity) helped a LOT. Sci really wonders about these women who are keeping these sponges in up to five days ANYWAY (I guess it wasn't as well known that you can get toxic shock syndrome from those kind of shenanigans).
4) And...what was present in the sponge that caused the odor?
Sperm of course. Or rather, ejaculate. The sponges had spermacide in them, obviously, but of course the spermacide caused the sperm to break DOWN. And that broke down a couple of major components of sperm, putrecine, spermine, and spermidine (creative names, right?) into some not so fresh smelling compounds. They determined this by obtaining some freshly used sponges (that must have been a great part of the study "hey, go put this is, get it on, and come back immediately, please, we'll need that spunk"), and leaving them out for a few days, discovering in the process that a 5 day "incubation" results in some seriously funky spunk.
The study concluded that ejaculate is the major cause of stinkiness in collagen sponges.
Of course, this IS 1978, but Sci still felt her jaw drop a little at this one. I mean, who keeps a sponge up in there for up to 12 DAYS!? Who would keep a contraceptive in there for up to five days AFTER sex without at least taking it out and washing it?! And most important of all, what lady noticed a smell and DIDN'T think "hey, maybe I should take out that sponge"?!?
And apparently taking the sponge out, rinsing it, and putting it back in is helpful for the odor, but Sci has to wonder about whether that spermacide will be as effective after a few washes (probably not).
But there's a particularly important take home message here. And that's this: vaginal malodor may not be the woman's fault if a sponge is involved. Maybe you can blame it on some funky spunk.
Chvapil, M., Chvapil, T., & Eskelson, C. (1978). Studies on vaginal malodor Archiv f�r Gyn�kologie, 225 (2), 77-89 DOI: 10.1007/BF00670844

40 responses so far

  • razib says:

    dude. this is definitely going in tomorrow's link roundup....

  • Jason says:

    Me too. You are my hero.

  • Suasn R says:

    Active or not, these smelly chicks are nasty and don't wash. Any part of the body left uncleaned will start to smell after a day or two, add moistness and you've got a powerful natural (or unnatural)deterrent.

  • Jefrir says:

    Active or not, these smelly chicks are nasty and don't wash. Any part of the body left uncleaned will start to smell after a day or two, add moistness and you've got a powerful natural (or unnatural)deterrent.

    Um, washing inside the vagina is generally a bad move

  • Cnonymous Aoward says:

    Any possibility that the smell is meant to deter other males, some sort of aid so that the first male's sperm wins?
    Where's an evolutionary biologist when you need 'em?

  • Stephanie Z says:

    Putrecine? Really?!? Why did they even have to look any further? 🙂
    On TSS, yes, it was named the same year this study came out and not generally known by the public until a couple years after.

  • Penelope says:

    I have a neighbor(I PROMISE it's not me)who told me the other day that she bathes only once or twice a month (!!) ... and she has a live-in boyfriend. Now I'm wondering how her man can stand to get near her business.

  • Vic B says:

    After hearing stories from the nurses at the doctors practice were I work I am not at all surprised at women keeping a sponge in there for 12 days! Things our nurses have found during cervical smear (PAP) tests include not one but TWO tampons and a used condom. The latter patient replied 'oh I wondered where that went'. Yuk.

  • Leni says:

    Pascale and I both had cause to wonder what poor grad student got THAT job.

    This made me laugh out loud. Poor bastard!
    Putrecine made me laugh too. I think I just found the perfect name for my next necromancer character in Guild Wars 😉
    @ Jefrir, sorry for over-sharing, but I always do after sex. Bad things happen if you don't, trust me. I'm pretty sure using a small amount of a mild cleanser (such as a douche made specifically for this purpose), rinsing well and not doing it too frequently is perfectly safe. Maybe it's not, but I've been doing it for two decades and haven't had a problem.

  • NJ says:

    Maybe you can blame it on some funky spunk.

    So...it's not the sponge, it's the spooge?

  • MT says:

    @9 Bad things happen? So I've only had a regular partner for 11 years instead of 20, but I have never, ever used any form of douche and have never seen any "bad things".

  • PalMD says:

    Brilliant as usual, Sci.
    A vaginal pH of > 4.5 is nearly always abnormal. We use pH to help diagnose bacterial vaginosis. I'll have to peek at the paper and see if they looked for BV, as sexual activity is a common precipitant of BV.

  • stripey_cat says:

    I was taught that vaginal douches increase your risk of getting diseases (both headline STDs and infections from out-of-balance bacterial populations), and were something you should basically never do. Of course, this was school sex-ed, so I'd be interested to see if there is actually any research to back it up.

  • senojjones says:

    I do this for a living.. Semen has a basic pH, and in the presence of bacteria like Gardnerella, short chained aliphatic amines like putrecine or cadavarine can be released.
    Normal vaginal has a pleasant yogurt like odor. Fishy is bad, and since it may be the result of a sexually transmitted organism like trichomonas, should be evaluated by a professional, like me. (Don't do this at home kids)
    #13, Douching is bad, since it destroys the normal flora, allowing opportunistic anearobes to just move in and set up shop.
    In general women have a fabulous natural scent, (they made a movie about it).

  • Pascale says:

    Great post, Sci!
    We share clinic space with the cystic fibrosis people who get sperm analyses on their teenage male patients. When one shows up in the printer, the first line is always "Odor." Apparently "musty" is the "normal" value.
    My nurses and I always get a kick out of this, because everyone wonders how we can stand to handle urine while some poor shmo in the lab has to smell jizz for a living.

  • Simile says:

    92% effective? % of what, and what percentage is a condom?. I remember reading somewhere that this was the percentage of couples that wouldn't conceive using the method over the course of a year, assuming they have sex three times a week. But an 8% risk every year for ten years seems an awful lot...
    P.S.
    Susan R is a tool of the soap industry I'm sure. They must employ thousands of minions all over the interwebs to secretly try encouraging people to buy soap. There are actually few parts of the body that smell all that bad after a few days unwashed; the hair and the armpits mostly I'd say. The lady's bits are most of the time pretty much self cleaning, and real men don't find Lactobacillus acidophilus a deterrent.

  • Art says:

    IMHO it isn't all that surprising. Lots of women were taught that their vagina is dirty, both physically and metaphysical level. They were not supposed to touch, talk about or even think about it. Sex was expected to be a simple matter of laying back, letting a man have his way. Mistral cycles involve doing the absolute minimum to keep evil vagina stuff from contaminating clothing and surroundings.
    It isn't all that bad medically, short of failing to remove foreign objects, like condoms and sponges, because the vagina is pretty much self cleaning. Just keep the outside clean and avoid inserting stuff and you're good to go.
    Of course as soon as you start stuffing things in you get a lot of reasons, smell being the least compelling, to making sure they are clean before insertion and come out afterward. But given the context of practiced, strongly culturally and morally reinforced, inattention it can't be surprising that the requirement to physically remove objects gets neglected.
    It may boggle the mind if you assume the ladies involved in this neglect were comfortable with and fully aware of their body but if you assume they are not then the situation pretty much explains itself. Ignorance, the taboo of talking about 'lady parts', and association with "filth" makes their behavior predictable.

  • Katie says:

    #16:

    92% effective? % of what, and what percentage is a condom?. I remember reading somewhere that this was the percentage of couples that wouldn't conceive using the method over the course of a year, assuming they have sex three times a week.

    Perfect use condoms are 97% effective, typical use they're around 88%. And that 92% figure you're thinking of is the number of couples that will get pregnant in a year of unprotected regular sex, not the number that won't.

  • That artfully posed flower and contraceptive is amazing. Nice work marketing department, you are ridiculous.

  • Leni says:

    @9 Bad things happen? So I've only had a regular partner for 11 years instead of 20, but I have never, ever used any form of douche and have never seen any "bad things".

    I was being tongue-in-cheek and didn't want to go into detail about it. Of course you are correct and nothing terrible happens. But I do wash with plain water nearly every time. Not because my vagina is bad, but because old semen is not the most pleasant thing in the world and I'd rather be rid of it. That's just my preference, though. I suggested douche because women do use them and they aren't harmful so long as they aren't overused.

  • Monica says:

    First off, congratulations on attaining your Ph.D, Doctor Sci!
    Ah, vaginal odors- reminds me of a paper referenced by my Endocrinology professor 'The' John Anderson- pretty sure I even sent it your way? WAY way back in the day. Anyhow, "Changes in the intensity and pleasantness of human vaginal odors during the menstrual cycle" by Doty et al. 1975. Science.
    "Something is funky down south" brings to mind "Something is rotten in the state of Denmark". or maybe that's taking things a bit too far...

  • jim says:

    "mid range pH of 5.5 is considered best."
    I wonder why. Neutral pH is 7, not 5.5, so I don't see why anyone would use a sponge with an acidic pH inside...
    Same goes for Dove soaps. Neutral pH is 7, not 5.5

  • Sesli says:

    I was taught that vaginal douches increase your risk of getting diseases (both headline STDs and infections from out-of-balance bacterial populations), and were something you should basically never do. Of course, this was school sex-ed, so I'd be interested to see if there is actually any research to back it up.

  • daedalus2u says:

    Acid pH is the natural state of the vagina. Anything above 4.5 is abnormal. That low pH is one of the normal protective mechanisms. Infectious bacteria like it neutral or slightly alkaline.
    A fishy or ammonia-like smell is a sign of a high pH. At low pH (less than 6 or so), all the ammmonia is present as ammonium and is non-volatile. The amines (that fishy smell is from amines) also form cations at low pH which suppresses their volatility.
    Many infectious bacteria break down urea (an abundant component of all bodily fluids) forming ammonia which raises the pH. That is true everywhere. The skin is also normally acid with a pH ~4 to 5. Skin pH goes up when it gets infected.
    The normal vaginal flora are mostly lactic acid bacteria which generate lactic acid and a low pH. Some of them also produce hydrogen peroxide.
    It is not true that not bathing always results in body odor. If you maintain a low skin pH, and the "right" skin flora, the odor causing bacteria are suppressed. The problem is that the "right" flora are slow growing and the wrong bacteria are fast growing. If you bathe frequently enough to get rid of the wrong bacteria you are bathing too frequently for the right bacteria to become established.
    What you want on your skin is the normal climax species that humans had in the "wild", not the "weeds" that grow back fast when the skin is clear-cut.
    Disrupting the normal flora is why often a yeast infection follows from a course of antibiotics. The antibiotics knock-out the normal commensals that are keeping the yeast in check.

  • After I originally left a comment I appear to have clicked on the -Notify me when new comments are added- checkbox and now every time a comment is added I recieve 4 emails with the same comment. Perhaps there is a way you are able to remove me from that service? Thanks a lot!

  • Greg says:

    Does this mean if my girlfriend's vagina smells unpleasant (and i'm not ejaculating inside of her) she is likely getting ejaculate from somewhere else? She's on birth control, so not exactly a sponge scenario.

  • Greg says:

    email me the answer gfrant7@gmail.com or theories

  • Ashley says:

    Those of you responding saying the vagina is self cleansing and cleaning inside your vagina is not good I would hate to be the guy having sex with you. I do, and have for 10 years, cleaned inside my vagina with soap everyday. The only time I ever have a yeast infection is when I take antibiotics for something and even then they are very mild and resolve themselves. I'm sure your "self cleansing" vagina has a lovely paste feel to it while my "actually cleansed" vagina is nice and fresh. Simile I guess you are the anti soap tool.

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