If you’ve ever (even for a short while) lost your sense of smell – it may have been with early covid, but it could have been due to a heavy cold – then you’ll understand how disorienting it can be.

We know that smell is deeply embedded in our brains and linked inextricably to memory. But it now appears that smell forms an intrinsic part of a person’s identity: scents are not only important in our relationship to food and the natural world but they also play a role in how we communicate with people we know.

A 2023 study from European researchers found that not only can we pick up the scent of other people’s fear or anxiety, but such emotions affect how we feel, too. Another study from China showed that people with better olfaction have more friends.

Humans have a long history of disregarding our noses—even Darwin claimed that the sense of smell is of “extremely slight service” to people. It appears that ‘social olfaction’ happens outside of our conscious attentionand the only thing you pick up on is that your body feeling changes. But you can’t quite put your finger on what it is…Yet humans seem quite able to pick out someone else’s body odour. One study found that after shaking hands with people of the same gender, people reflexively sniffed their right hand more than twice as often as they did before the greeting.

We pick up quite a lot of information from sniffing the body odour of people around us: we can recognise our relatives, tell who is genetically related and pinpoint potential friends (apparently we tend to choose friends who are genetically similar to us and have similar body odour). In one study, most new mothers were able to identify their baby by its smell after spending as little as 10 minutes together, and newborns can recognise their mother, too.

Adult human sniffers, meanwhile, can match pairs of identical twins by their body odour, even if the siblings live apart. In a 2022 study, researchers at the Weizmann Institute of Science managed to predict which volunteers would bond together simply by comparing their body odour—a task performed both by human smellers and an electronic nose (a device that looks like an old CB radio with a hose). The scientists discovered that people who smelled similar to each other were more likely to enjoy chatting and report that they felt instant chemistry. This goes along with earlier research showing that we subconsciously choose friends who share some of the same genes.

What’s more, if we were to chat with someone feeling happy, chances are we would detect their current emotional state through smells that reach the nose. In one experiment conducted in the Netherlands, volunteers watched cheerful videos while holding absorbent pads in their armpits. Later, when another group sniffed the pads, measurements of their facial muscles’ activity revealed that their mood improved, too: their smile muscles moved more.

Yet it’s not only happy feelings that can be communicated through body odour. A 2020 study by Pause and colleagues showed that women’s brains reacted more strongly when they smelled the sweat of men who had played an aggressively competitive game compared with the odours of men who had just enjoyed a calm construction game. It turns out that women also proved to be particularly sensitive to odours that signaled male anxiety. On picking up such odours, they became more risk-avoidant and less trusting. Anxiety is a signal of, ‘Please, I need help.” This may explain why women appear more attuned to the smell of anxiety—historically, in distressing situations, it was women that cared for the young and the feeble. Such evolutionary links could also explain why women with more discerning noses perform better at tests of empathy, as revealed in a small 2022 study carried out by Pause and her colleagues.

In general, a sensitive nose seems to be an asset that enhances our deeply social life. Those who could better tell apart everyday odours also reported less loneliness, a 2020 study of 221 volunteers concluded. In other experiments, people with a better sense of smell had a larger social network and more friends, and they met with those friends more often. Functional magnetic resonance imaging of the brain, meanwhile, revealed that the same brain circuits may be involved in both our sense of smell and the size of our social circle.

For now, however, the mechanisms of how exactly humans pick up body odours and translate them into changes in our behaviours remain largely a mystery. Scientists are also just beginning to pinpoint which chemicals in body odour may be responsible for influencing social connections. One such molecule may be hexanal, which gives off a pleasant whiff of freshly cut grass—and appears to boost trust in people. Yet we still don’t know if those who have more hexanal in their body odour are perceived as more trustworthy, says Monique Smeets, a social psychologist at Utrecht University in the Netherlands.

More research will likely follow because, the covid pandemic really put a spotlight on the sense of smell. Even though Omicron appears to be less damaging to our noses than previous COVID variants were, a 2023 study estimated that 11.7 percent of adults of European ancestry who have been infected with Omicron have had some amount of olfactory dysfunction. People with smell loss may end up missing out on important but subconscious ways of communicating with others. And smell should be valued because olfaction is the most honest of our senses—something that, unlike our words or facial expressions, we just can’t fake. We can laugh even though we’re sad or aggressive, but we cannot intentionally change our chemical messages. It’s information which you can really trust!

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