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.

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