Sex, Stink, Science, and Kink: A New Understanding of the Complex Chemistry of Our Armpits
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Scientists have a new understanding of how and why the complex biome contained in our armpits exists and the critical function they play in our health.
Despite recent stories that have highlighted the trend of celebrities and others to stop wearing deodorant all together, or that gay men can identify each other by that smell, or that gay men in general just love “man musk,” or even that men and women smell vastly different, scientists now have uncovered evidence that the odor developed as a survival mechanism from a proto-human ancestor.
According to the latest issue of the journal Science News for Students:
Sweat keeps us cool. But the stuff that seeps out from our armpits can create a powerful stink. Deodorants can help combat that odor. But to really tackle it, we first need to know what causes it. A new study finds that bacteria found only in our armpits make an enzyme that turns our sweat into smelly B.O.
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Glands in our skin make two types of sweat. Eccrine (EK-kreen) glands located all over the body release watery sweat. It cools us as it evaporates. Apocrine (APP-oh-kreen) glands under our arms and in our private parts also release liquid. Although it might seem like garden variety sweat, it’s different from the watery eccrine type.
The apocrine liquid doesn’t actually stink. In fact, it doesn’t have any odor. But when nearby bacteria go to work, that sweat takes on a distinctive foul scent.
Michelle Rudden and Gavin Thomas wanted to know how apocrine sweat turns into that off-putting body odor. These biologists work at the University of York in England. Two years ago, their team identified the bacteria responsible for creating body odor. Many species of staphylococci (STAF-ih-luh-KOK-ee) live on our bodies. But this team turned up one that lives only where there are apocrine glands. Called Staphylococcus hominis (STAF-ih-luh-KOK-us HOM-in-iss), it’s even named for us. (That hominis refers to humans.)
Enzymes are molecules that drive reactions. Rudden and Thomas were looking for an enzyme that would break down apocrine sweat. This could release compounds that might move through the air — right to someone’s nose. To find it, they teamed up with York chemist Anthony Wilkinson. They wanted to find the enzyme that releases a thiol (THY-oll) called 3M3SH. This molecule creates the tangy, acrid smell that is the hallmark of B.O.
Exactly what makes thiols so stinky is a mystery, Rudden says. But it’s related to the sulfur atom in the molecule — the “S” in 3M3SH. “By itself, sulfur is odorless,” she says. But when bonded to another atom, it can give rise to an unpleasant scent. Our noses have what amounts to “a chemical sensor” to detect it, Rudden notes. Those receptors have played an important role in our history, she adds. They let our ancestors “sniff out rotten food or potential poisons,” she explains.
“B.O. may have been an important communication molecule among ancient primates,” Rudden says. But it doesn’t seem to benefit modern humans, she adds. Our underarm stink may well be an “evolutionary hangover” from our ancient ancestors.
The team described its findings in Scientific Reports on July 27.
This study shows “there is always something new to learn,” says Sylvie Garneau-Tsodikova. She is a microbiologist and biochemist at the University of Kentucky in Lexington. She also finds it interesting that this stinky body odor has been around longer than humans have existed as a species.
Now that the York team has identified the chemistry of human body odor, they can develop new types of deodorants, says Rudden. These will “stop B.O. production at the source without disrupting the armpit microbiome.”
And keep in mind, Rudden quips, when it comes to stinky underarms, “It’s really not you — it’s your bacteria!”
