While our sense of smell mostly remains a mystery, there are some amazing facts we do know. Even if a couple are on the nose.



Right now, your body is producing all sorts of smells that convey different types of information. If you are sick or stressed, your body may emit a particular scent. Even certain personalities are linked to particular scents. While how we detect and analyse certain scents still remains a mystery, there’s a school of thought that suggests our scent is as unique as our fingerprint.

Psychologist and cognitive neuroscientist Dr Rachel Herz contends that smell is located in the same part of the brain that processes emotion, memory, and motivation. To our ancestors, the sense of smell wasn’t just important, it was crucial to their existence. Herz believes that very little has changed since then, and our “emotional, physical, even sexual lives are profoundly shaped by both our reactions to and interpretations of different smells.”

But how, exactly?

The answer lay in our genes. Specifically, genes in the major histocompatibility complex (MHC). MHC genes control how foreign molecules are presented to the immune system. While these genes usually detect disease-causing organisms, they also decide who we choose as a mate through body odour.

In 1995, Bern University academics devised a test in order to prove the hypothesis. Male volunteers were tasked to sleep in the same T-shirt for two nights. To avoid tainting the shirts with other aromas, they were asked not to use perfumed deodorants, avoid spicy food and alcohol, sleep alone and refrain from sex. After returning the t-shirts, the women in the test were asked to sniff them. As a result, they preferred the garments worn by men whose immune system genes did not match their own.

However, smell is more than just finding a mate.



The smell of age

While old people smell, but it is not a bad thing. A study from 2012 found that older participants (75 to 95 years old) had a distinct scent, which was not strong nor unpleasant—just characteristic of their age group.

“Elderly people have a discernible underarm odour that younger people consider to be fairly neutral and not very unpleasant,” said Johan Lundström, a sensory neuroscientist at the Monell Chemical Senses Center in Philadelphia, USA, who led the study, in a press release. “This was surprising given the popular conception of old age odour as disagreeable. However, it is possible that other sources of body odours, such as skin or breath, may have different qualities.”

The reason might have something to do with our evolution. “Similar to other animals, humans can extract signals from body odours that allow us to identify biological age, avoid sick individuals, pick a suitable partner and distinguish kin from non-kin,” said Johan.

This also holds true for babies. A 2013 study found that the smell of 2-day-old babies activates a special part of the brain associated with food, or hard drugs.

“What we have shown for the first time is that the odour of newborns, which is part of these signals, activates the neurological reward circuit in mothers. These circuits may especially be activated when you eat while being very hungry but also in a craving addict receiving his drug. It is in fact the sating of desire,” said Johannes Frasnelli, lead author of the study.



The scent of disease

Certain diseases seem to leave a particular odorous signature in the body of patients, which can be detected by a sensitive nose. In fact, dogs can even be trained to detect several human cancers (such as breastmelanomalungovarycolorectalbladder and prostate cancers), Parkinson’s disease and even COVID-19. Yay?

“The full potential of dogs to detect human disease is just beginning to be understood,” said Claire Guest, Chief Executive of Medical Detection Dogs in a 2017 news report. “For hundreds of years, dogs have guarded us, rescued us when we’re lost and provided unparalleled emotional support. Is it so hard to believe that they can detect the odour of human disease?” she asks.

“Dogs have an extraordinary sense of smell. They can detect parts per trillion—that’s the equivalent of one drop of sugar in two Olympic-sized swimming pools,” said Claire.

In 2016, the University of Liverpool and the University of the West of England (UWE) developed an apparatus (called Odoreader) that detects prostate cancer. Professor Norman Ratcliffe, who lead the study said, “There is currently no accurate test for prostate cancer, the vagaries of the PSA test indicators can sometimes result in unnecessary biopsies, resulting in psychological toll, risk of infection from the procedure and even sometimes missing cancer cases. Our aim is to create a test that avoids this procedure at initial diagnosis by detecting cancer in a non-invasive way by smelling the disease in men’s urine. A few years ago we did similar work to detect bladder cancer following a discovery that dogs could sniff out cancer. We have been using the Odoreader, which is like an electronic nose to sense cancer.”



The pong of personality

Here’s where it starts to get weird. A 2012 study proved that certain personalities could be identified purely from their scent, again through the medium of stinky t-shirts. This time, 60 participants were asked to wear a shirt for three days, with the resulting stench compared with the self-assessed personality tests filled in by the participants.

According to the researchers, “the results showed a strong relationship between odour and three personality types: extroversion, neuroticism and dominance.”

With that being said, those who believed themselves to be agreeable, conscientious and ope, did not seem to have any associated scent. My conclusion: not nice people stink.

With that being said,  a more contemporary study discovered that people who can’t handle body odours might be drawn to authoritarian figures.

In the study, researchers asked whether people’s sensitivity to body odour (labelled in the study as body odour disgust sensitivity, or BODS), was related to the intention of voting for Donald Trump. “We showed a positive association between BODS scores and support for Donald Trump, who, at the time of data collection, was a presidential candidate with an agenda described as resonating with authoritarian attitudes,” the authors said in their study.

So what is the logic here? The authors speculate that people who are more sensitive to body odours (high in BODS scores) may have a stronger fear of disease. Unknown folk, for example, could represent a potential source of disease in the mind of someone scoring high in BODS. It’s worth noting that this study was published in 2018, but I’ll love to see a post-COVID version.







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