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Meet Dr. Armpit, Changing Body Odor With Bacteria

What’s really happening under your arms? The secret to skin smells is all in the microbes.

Meet Dr. Armpit, Changing Body Odor With Bacteria
[Armpit: Alliance via Shutterstock]

Here’s an undeniable fact: In samples collected from seven of New York’s subway platforms, scientists discovered that we’re surrounded in plumes of microbes wafting off other people’s skin. Here’s another undeniable fact: Those bacteria colonize all of our glands and follicles and the entire epidermis. They make our skin smell. The scientific justification for l’eau de bacteria is that scents enabled great apes to sniff out those with optimal fitness and health, basically, find sex without the sickness.

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For most of us, though, the axillae are not beacons of communications; they are damp creases under our arms. They are sweat, they stink, we want to stop them. Or, better yet, smother everything with an olfactory bang of scented deodorants—a market so persistently robust that it almost never has to change.

So, then, in the world of underarm odor, “Dr. Armpit” is an outlier: He wants to solve body odor in a totally unusual way. I reached him one evening at his office in Ghent, Belgium. His real name is Chris Callewaert. He is 28 and is not quite a doctor. (The public defense of his doctorate dissertation is scheduled next month.)

“Everybody now gets rid of their bacteria in order to prevent odor,” he told me, “but maybe the solution all along is just to have bacteria there—good bacteria.”

During one recent test, he swabbed the underarms of nine test subjects—three times under the right, three times under the left. For a month, all nine of them stopped using deodorant and antiperspirants. Calleaert swabbed again and then extracted the DNA from all these swabs. His results were published last August. To a nation primed by Old Spice (“shoot lasers” at your “stench monsters”!) and no-soap hygiene experiments and rock salts advertised in the back pages of Harper’s magazine, or whatever it was, the study arrived as perversely welcome news. “Antiperspirants may actually make you smell worse,” a headline on the Washington Post read at the time.

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Over the short-term, antiperspirants stopped one problem but, over the long-term, they appeared to exacerbate another. When Callewaert took a census of bacteria, using the DNA sequences, some of his test subjects who’d been using antiperspirants had a greater diversity of bacteria. This, in turn, appeared to hasten the growth of foul-smelling microorganisms, such as corynebacteria, which are responsible for volatile compounds known for their pungent, sometimes repugnant odor.

This was not the first time scientists suggested a greater appreciation for the body’s under-appreciated inhabitants. In 1968, a researcher named Mary J. Marples wrote an essay in Scientific American, about the human skin. She compared the forearm as a desert and the head as a cool forest, and left us with enduring metaphors for the skin as an ecosystem—sort of like an overview effect of the underarm. (She also inspired a poem by W. H. Auden: “A Very Happy New Year/to all for whom my ectoderm/is as Middle-Earth to me…”) In this view, the armpit existed as an ecological niche: a dank, dark tropical rainforest. The article’s graphics depict homunculus with dark red armpits—representations of the intense heat and concentration of sweat glands and white, lipid-rich fluids that feed “very dense” populations of bacteria.

Scientists have since honed in on these organisms, pinpointing certain odors. As Callawart sees it, they’re all simply competing for the niche. “It’s a bit of bacterial warfare on the skin—or in the armpits. They are constantly fighting each other.” When certain organisms, such as staphylococcus, dominate, he told me, they might not create what we think of as body odor. Throw that equilibrium out of whack, though, and odor-causing bacteria can flourish. That happened, in some case, with antiperspirants. And, more recently, he’s found that synthetic, polyester fabrics can similarly harbor malodorous microbes moreso than cottons.

Finally, I asked Dr. Armpit (who, remember, is not actually a doctor) if he had any practical advice to smelling sweeter. He said you don’t necessary have to avoid deodorants and antiperspirants: There’s probably nothing wrong with a higher diversity of bacteria in your armpit. Could you pick up someone else’s scent by wearing their shirt? Should that be avoided? “That’s definitely possible,” he said. “I’ve heard stories about people who picked up their bad body odor by sleeping in a dirty bed…” If we’re all programmed to like the smell of healthy babies, I asked, could we somehow dab that scent on? “So it’s not going to be that easy, but it’s a great idea.” At this point, he said, the findings were still preliminary, yet another hint to develop testing that doesn’t stink.