They call sex “dirty.”

They are right.

Messing around is messy business, involving certain human juices that – during any fully clothed hour of the day – usually elicit at least a wince: saliva, sweat, semen, plus body odors. An intimate river of secretions. (Let’s see someone pen a love song using that title. We’re guessing Madonna is up for the challenge.)

They didn't dub it “bumpin' uglies” for nothing. But some of the physiological funk that accompanies sex begs a scientific question: How have eons of generations procreated, keeping the species alive, when reproduction requires us to either A) ignore certain bodily fluids or B) pretty much embrace them?

A new study conducted in the Netherlands offers a possible answer: Sexual arousal seems to dampen our natural disgust response. The findings were published Wednesday in the open access journal PLOS ONE. Lab tests blended porn and plastic bugs – but more on that lovely combo in a second. The researchers discovered that if you’re in the mood, love conquers all, even the stanky stuff, neurologically speaking.

“This (answers) the intriguing question of how people succeed in having pleasurable sex at all,” wrote the authors, led by Charmaine Borg of the University of Groningen in the Netherlands. “Sex and disgust are basic, evolutionary relevant functions that are often construed as paradoxical … and possibly obstructive.”

Even Sigmund Freud, who had a little something to say on sex, recognized this fact, writing: “A man, who will kiss a pretty girl’s mouth passionately, may perhaps be disgusted by the idea of using her toothbrush.” True that.

Ironically – at least to us – the Dutch team chose to test heterosexual females with an average age of 23 versus the horniest people on the planet: college dudes. The subjects, recruited from the University of Groningen, were assigned to one of three categories: “sexual arousal,”  “non-sexual, positive arousal,” and a neutral control group.

To stir the women into the desired states for the experiments, the “sexual arousal” subset was shown a 35-minute, “female friendly” erotic film – “de Gast” – which in Dutch means, “The Guest.” (Feel free to imagine the plotline but we’re assuming “the guest” was a really good listener and an excellent cuddler who swore that those jeans in no way made her butt look huge.) Meanwhile, the “positive arousal group” got to watch an adrenaline-rush movie on rafting, skydiving and mountain climbing. And the control group’s featured footage: a train trip offering natural scenery. (Zzzzzz.)

Researchers next asked all the women to complete 16 gross tasks, including sipping juice from a cup containing an insect (the bug was plastic) and wiping their hands with a "used" tissue (the snot was just colored ink).

The erotically revved women agreed to perform the highest percentage of repulsive jobs, the study reported. And they did those disagreeable duties “with less disgust than subjects who were not sexually aroused,” the authors wrote, “suggesting that the state of arousal has some effect on women's disgust response.”

Following their volunteer work, the lascivious ladies were supplied with “refreshments” then handed a parting gift: 10 Euros. In Amsterdam, apparently that's the traditional culmination of “date night.” 

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