From our head to our toes, we each have our own unique odors. Some are pleasant — like the top of a baby's head or your husband's neck when you hug him. Others? Decidedly not. But even the scents we consider unsavory are completely natural. As extensive "psychology of smell" research indicates, these odors may even be useful to us, just as they were to our much reekier prehistoric ancestors.
At some point in our early history, smelling each other may have been as central to our social interactions as recognizing faces or hearing voices. "There are powerful chemicals in underarm sweat," says George Preti, PhD, an organic chemist at the Monell Chemical Senses Center in Philadelphia who studies human odor. And while most of us today try to avoid sweating in public, those chemicals served a purpose in human evolution: providing warning signals or important cues to anyone who caught a whiff. Other animals, after all, use scent to communicate with each other in myriad ways, from marking territory to scaring off predators. Why not us?
Science suggests body odors may help bond families, communicate things about our health (like, for instance, whether we're ovulating), and may tip us off when people are lying or angry. They could even inspire us to seek out a new friend from, say, the next voting booth: A recent study found that people may prefer the scent of those who hold the same political views they do.
This is strong stuff, driven by a simple biological process. Contrary to popular belief, sweat itself doesn't smell. B.O. happens because bacteria that live on our skin feed on fats and proteins in our perspiration; as they break down those molecules, stinky chemicals are released.
Despite the ick factor, there's nothing unhealthy going on, says microbiologist Chris Callewaert, PhD, a body odor researcher at Ghent University in Belgium, who gamely calls himself Dr. Armpit. "Bacteria on our skin, including those in the underarm, are in fact good for you," he says. These friendly bugs fight off germs that could cause infection and may help reduce skin inflammation and irritation in general, studies suggest.
So B.O. comes with benefits, but we know: It still stinks. And the paranoia we all feel about offending other noses is even worse than whatever may waft from our bodies. Enough worrying and wondering. Check out our guide to fresheners for your smelliest body parts — we tested store-bought and natural deodorants.
A Cultural Love of Clean
We're social animals. No one wants to repel others with their funk. The global deodorant market is now booming; but judging by the evidence, Americans are most obsessed with body odor. Case in point? A modern guidebook for new immigrants and exchange students advises readers: "If your culture does not equate floral…scents with cleanliness and health, then some Americans…will probably think you 'smell funny.' " To make friends and fit in, writes the author, "try to smell like soap." Welcome to the United States of Antiperspirants, y'all.
We weren't always so uptight. Our cultural fixation with staying dry and smelling fresh dates back only to the early 20th century. Up until then, perspiration was considered a perfectly acceptable part of being human. But in 1912, the daughter of a surgeon who created an aluminum-based product to stop his hands from sweating during operations realized that the paste could also keep her underarms dry. She started marketing it to women as an antiperspirant (the formula was called Odorono — as in, "Odor? Oh, no!"), says Katherine Ashenburg, PhD, a social history researcher and author of the book The Dirt on Clean: An Unsanitized History. Just like that, perspiration became a cause of insecurity and embarrassment. Proof? By 1927, Odorono had reached a whopping $1 million in annual sales, and an industry was born.
Different Levels of Stink
We've been using antiperspirant and deodorant for 100 years, but it turns out that not everyone needs to be dousing themselves with the stuff. Experts say that some people naturally smell worse than others, while a lucky two percent of women — and an even higher percentage of people of East Asian descent — have little to no B.O. Their genetic makeup means they don't need to slather on deodorant, but interestingly, the researchers found that the vast majority still do. (Stink paranoia? Perhaps — or maybe just a culture-wide habit.)
The other 98 percent of us smell for many reasons, including stress and diet. If you eat a lot of meat, for example, you may be stinkier than a vegetarian friend. And scented chemical compounds from foods like garlic can also seep out in your sweat. Ditto for alcohol, caffeine, onions, and spicy foods that could bring your body temperature up, like hot peppers or curry. Cutting back on these culprits might help tone down your personal pungency.
We humans can also blame our odors on the balance of bacteria in our underarms. And you might be more "stink dominant" on one side of your body: "Research shows that about half of people have differences in the types of bacteria that live under their left and right arms," says Callewaert. This may be because the arm you use most gets more blood circulation — and sweat.
As far as bacterial balance is concerned, some people seem "preconditioned" for extra pungency. In a recent study, Callewaert swabbed a pair of twins' armpits and found that the stinkier one had a higher concentration of corynebacteria, the germs that produce that oniony scent. In an unusual example of brotherly love, Dr. Armpit "cured" him by reseeding his underarms with a bacteria sample from his sweeter-smelling twin.
Callewaert tried it on the twin after experimenting on himself — this is actually how he became Dr. Armpit in the first place: "I noticed that my own body odor changed from one day to another, and when I started looking into the research on it, I realized that there were still a lot of unknowns. So I eventually did my PhD thesis on body odor. Along the way, I got rid of my own through a transplant of underarm bacteria. That convinced me to try it on other people." So far, there's no sign of transplants becoming the deodorant of the future, but don't be surprised if you begin to hear more about the method.
Why Stress (Really) Stinks
If you've ever noticed something funny in the air at particularly tense moments, you're not imagining it. When we're stressed out, our odor changes, says recent research. That's because we have two different kinds of sweat glands that kick in at different times and for different reasons.
The eccrine glands are all over our bodies and spurt bits of salty water onto the skin's surface to help cool us off when we get warm. Apocrine glands, on the other hand, are concentrated in hairy spots like the underarms and groin. Neither type of sweat smells on its own, but the apocrine glands put out a milky fluid packed with fats, amino acids, and proteins that odor-producing bacteria love to feast on — and these glands rev up when you're stressed or scared. So, after a job interview, for example, you might wonder if you forgot to use deodorant. (Nope, it's just nerves.) Why do our bodies betray us this way? "It may be a response shaped by evolution to keep us from being eaten," says Richard Doty, PhD, director of the Smell and Taste Center at the University of Pennsylvania. "In some animals, those glands activate in order to protect against or repel predators, or possibly to signal others around us that there's danger."
Think of how much worse we must have smelled when we were facing saber-toothed tigers rather than cranky HR people. Whatever your day holds, you'll find solutions. Seriously, people — don't sweat it.
This story originally appeared in the March 2016 issue of Dr. Oz The Good Life.
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