Why Do I Like the Smell of My Boyfriend’s Body Odor?

Science justifies your disgusting predilections.

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Nov 22 2016, 3:00pm

Image: Lukasz Wierbowski

Ah, friends. They're like family but cooler. Fully customizable. Fall and one of them will be right there to pick you back up. But as great as friends can be, they also do a lot of really stupid stuff. Stuff that blows your mind. Like, sometimes it seems crazy that you even hang out with people who make such crappy decisions. Stuff that, were it to get out, would be mortifying for anyone with even a shred of self-respect. Lucky for your friends, they've got you to ask their deepest, darkest questions for them. And lucky for you, we started this new column to answer those most embarrassing of queries.

The scenario: Your "friend" likes to catch a whiff of her sig fig's sweet underarm secretions. She even asks him not to shower and get in some light physical activity—say, chopping lumber in a plaid flannel shirt—for a of couple hours just so she can bask in his glorious scent. But just last week she sent you a text (or hm was it you who sent it to her?) complaining about a pungent individual on the subway sporting enormous stains. According to her, the stench was "pungent AF" and she had to change cars ASAP. Hold up lady, aren't you the one who seeks out body odor? 

What's happening: Per science, your friend is pretty normal. Humans can learn to tolerate, and even appreciate, our partners' personal fragrance for a variety of reasons. 

So what comes first, the person or the pits? Are we drawn to someone's underarms "instinctively" or does the appreciation build up over time? Experts think it's a little bit of both. Some research has found that people, especially women, can sniff out "better" mates through body odor alone. One oft-cited study had 49 women smell men's two-day old shirts and found that they strongly preferred the spices of those who possessed different gene variants from them. Experts theorize that this allows sex partners to create offspring that are more genetically diverse. And when the genetic makeup of your immune system is more diverse, you can presumably ward off more diseases, says Pamela Dalton, a researcher at Monell Chemical Senses Center in Philadelphia. Though it's not the end all, be all in every relationship, she adds that in general, smell seems to be more important for the ladies. "It makes sense: Since women are investing more time and effort in reproduction, they would want to make sure their offspring is as healthy as possible." In other words, don't feel bad that you blew off a Tinder prospect due to his mediocre funk—you were just looking out for your kin.  

Guys, meanwhile, aren't so far behind. In another study, 41 women were asked to wear cotton gauze pads in their pits for 24 hours on two different days—a high-fertility day (just before ovulating) and once on a low-fertility day. (Btw, they all had regular menstrual cycles and were not using any contraceptives or medications that contained hormones.) Their resulting sweat pads were rated by 112 straight men in the name of science. "Men rated women's high-fertility scent samples as smelling sexier and more pleasant than their low-fertility samples," says study author Kelly Gildersleeve, assistant professor of health psychology at Chapman University. "It could be a learned response that historically encouraged men to have sex with a woman precisely when sex was more likely to result in conception." 

How does your nose know that your partner and you are a match made in Charles Darwin's heaven? Per Gildersleeve, the theory is that through body odor, you're detecting their major histocompatibility complex (MHC), a set of genes that plays a critically important role in helping our immune system identify and defend our body against pathogens, and are thought to be closely connected to those that dictate body odor. 

These studies are small and not conclusive, so more research needs to be done to confirm if body odor and gene policing are in fact linked. But we do know that scent and bonding are very much related. Having a strong connection with someone and being attracted to them can nudge us to appreciate their scent even more—and this applies to couples of all sexual orientations (most of the work on MHC has been done on straight individuals). "When you're in a relationship, the smell of your partner becomes a way to identify with that person even if you're not always fully aware of it," explains Dalton. "Their scent becomes comforting and a source of positive feelings, so you come to enjoy it. In fact, when people lose their sense of smell, what they find most distressing is not being able to detect the scent of loved ones." 

About the dude on the subway: Your friend is predictable in her choosiness about which flavor of B.O. turns her on and which she turns her nose up at, according to a study published this year in the Proceedings of the National Academy of Sciences. Researchers ran two experiments in which they invited students to sniff a T-shirt with stale sweat, either bearing their university's logo, another university's logo, or no logo at all. "Consistently we found that when participants thought the smelly shirt belonged to in-group members, they found it less disgusting than one apparently belonging to an out-group member or another individual," explains study author John Drury, deputy director of research and knowledge exchange at the University of Sussex. "This told us that what has up to now been considered relatively fixed—the disgust response to a horrible smell—can become attenuated by social relationships. We feel less disgust if 'they' are 'us.' Importantly, the same person can be in-group or out-group depending on context, so this really shows how socially malleable disgust is." Studies have even found that mothers think their baby's dirty diapers smell a little bit less gross than those of other tots. Equal parts cute and gross, the findings point to a truism: when it comes to love, you can't fake the funk.