If You Don’t Like The Way Your Boyfriend Naturally Smells, You Should Break Up—Here’s Why

It may seem fickle to end a relationship based on someone’s smell, but dating someone who doesn’t have a compatible odor has a variety of consequences – so much so, it can even affect your offspring. Here’s why.

By Rebecca Hope3 min read
Pexels/Ron Lach

Have you ever gotten the ick with someone and not understood why? Maybe the guy you’re thinking about ticked all the right boxes – he’s handsome, successful, and kind – yet still, there was something about him that simply repelled you? It’s totally possible it was his smell that turned you off! 

Even Edward Cullen was aware of this biological instinct: “Everything about me invites you in – my voice, my face, even my smell,” he says to Bella. And it seems we humans lure potential suitors in a similar way. Although odor compatibility may sound a little ridiculous, according to psychologist Rachel Herz, “One of the most common things women tell marriage counselors is, ‘I can’t stand his smell,’” so it’s definitely worth paying attention to.

Of course, men are sensitive to smell also, but to a lesser extent. As researchers learn more about this area, it seems that much of what we call “sexual chemistry” is a direct result of scent-based compatibility. 

This is one of the mysteries of sexual attraction – perhaps that “icky” feeling may just be an instinct alerting you to the fact that that guy (despite how great he might be) is just not the most compatible partner for you biologically.

His Scent Should Be a Turn On

If his scent isn’t a turn on for you, it could be your instincts telling you he isn’t the one. This instinct operates on a very subtle level, but research shows we use scent-based signaling mechanisms to work out our compatibility with another person. For example, let’s take a look at Claus Wedekind’s study from 1995.

The T-Shirt Test

Claus Wedekind is a professor at the University of Lausanne in Switzerland. He conducted a study involving 44 men to whom he gave a new T-shirt to and told them to wear the shirt for two nights in a row. To ensure the scent on the shirt wouldn’t be affected by toiletries, he gave the men fragrance-free soap and aftershave.

Once the shirts were taken off, 49 women sniffed the shirts and specified which odors they preferred the most. The results showed that women were more attracted to the smell of the T-shirts worn by men who were immunologically dissimilar to them. This dissimilarity was shown in the sequence of more than 100 immune system genes known as the major histocompatibility complex (or MHC). These genes code for proteins that help the immune system identify pathogens. The women who participated in the study also said the odor of their favorite smelling shirt reminded them of their past and current boyfriends. This further suggested that MHC does influence a woman’s dating decisions.

By choosing a man with a dissimilar MHC profile, a woman also chooses a man with a different immune system. Not only does this protect her from pathogens, but it also protects her children. This is because partners whose immune systems are different produce offspring that have a greater protection against a wider variety of pathogens.

Women on the Pill

Although women generally prefer the smell of men whose MHC profile is different from their own, Wedekind’s study revealed one exception to this rule – women on the birth control pill. When women on the pill sniffed the T-shirts, it had a completely opposite effect. Pill users preferred men whose MHC profiles were similar to theirs.

This is most likely because the pill prevents the ovaries from releasing an egg and fools the body into thinking it’s pregnant. When a woman is pregnant, she’s in a very vulnerable state, so in this situation, she may have a preference for kin and those who are genetically similar to her. Instinctively, she may feel these people are more likely to help protect her unborn child.

According to Herz, choosing your partner on the pill is like “picking your cousins as marriage partners.” And as a result of picking your partner on the pill, you may find that you are less attracted to your husband when you come off birth control to try for a baby. This sudden lack of attraction could be your brain telling you that you’ve made a mistake and married the wrong guy genetically.

What Happens When We Choose Partners That Are Too Similar to Us?

Your MHC profile is as distinct as your fingerprint. A potential suitor who smells good to one woman may completely repel another. Herz says, "There's no Brad Pitt of smell … Body odor is an external manifestation of the immune system, and the smells we think are attractive come from the people who are most genetically compatible with us."

Usually, our noses guide us in the right direction of picking a compatible partner, but if this fails us, we may end up picking a mate whose MHC profile is too similar to our own. Couples with a high degree of MHC similarity suffer longer intervals between pregnancies and higher rates of miscarriage. This was shown in a study conducted by Carol Ober, a geneticist at the University of Chicago. 

Ober studied members of the Hutterite religious clan, a closed society that has around 40,000 members. Hutterites only marry other members of their clan, meaning the variety in their gene pool is quite low. Most women in this society still manage to find partners who have a dissimilar MHC profile than themselves; however, the few couples that did have a high degree of MHC similarity struggled with the infertility issues mentioned above.

The Pill Makes Women Appear Less Attractive

Not only does the pill confuse a woman’s ability to identify a compatible partner, but it may also affect the scent messages she sends to men, making her less appealing to potential partners.

Evolutionary psychologist Geoffrey Miller noticed a connection between the pill and waning male desire while studying a group of exotic dancers. Miller found that non-pill-using dancers made around 50% more in tips than dancers on oral birth control.

In Miller’s study, the women off the birth control pill were the biggest earners during ovulation. Miller therefore believes that it’s likely that women are doing something unconsciously, such as releasing pheromones, and men are responding to it. 

Closing Thoughts

If you’re single and looking for a partner, it’s time to follow your nose and get off the pill. The first few weeks of a relationship are essential to assessing compatibility, and if you’re on the pill in the initial stages, it’ll become harder to decipher if the guy is right for you or not.

However, it’s important to keep this in context. Although you may have great scent compatibility with a guy, this shouldn’t supersede how he treats you. It’s important to find the right balance, so if he smells great but isn’t treating you great, he’s not the guy for you. But don’t worry if you sometimes find your partner’s scent off-putting – it doesn’t necessarily mean you’ll struggle to conceive. These findings are yet to be confirmed with further studies.

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