Body odor may subconsciously change how people interact

Researchers at the University of Tokyo have discovered that scent cues from women during ovulation may shape how men perceive them. This isn’t about myths or love potions. It’s about biology in action. The team found that certain compounds in female body odor increase during ovulation.

When these were mixed with armpit odor samples, men rated the scent as more pleasant. They also viewed associated images of women as more attractive and more feminine. Additionally, these scents appeared to reduce stress, based on lower levels of the biomarker amylase in saliva.

The team emphasized this is not proof of pheromones in humans. But it suggests smell might quietly influence how people relate to each other.

Human pheromones still uncertain

Pheromones – behavior-altering chemicals shared between organisms – are a popular staple in pop culture, especially romantic comedies. Despite the fun storylines, their existence in humans has not been definitively proven.

However, a new study from the University of Tokyo does show something measurable and interesting is happening – something that parallels the idea of pheromones.

“We identified three body odor components that increased during women’s ovulatory periods. When men sniffed a mix of those compounds and a model armpit odor, they reported those samples as less unpleasant, and accompanying images of women as more attractive and more feminine,” said Professor Kazushige Touhara.

“Furthermore, those compounds were found to relax the male subjects, compared to a control, and even suppressed the increase in the amount of amylase (a stress biomarker) in their saliva. These results suggest that body odor may in some way contribute to communication between men and women.”

Ovulation changes body odor

Previous studies by various research groups found that female body odor changes throughout the menstrual cycle. During the ovulatory phase, these changes can be detected by men and are often described as pleasant. However, the exact nature of these odors remained unknown.

To investigate, Touhara and his team used a technique for chemical analysis called gas chromatography-mass spectrometry and identified volatile compounds that fluctuate across menstrual cycle phases.

“The most difficult part of the study was to determine the axillary (armpit) odor profile within a woman’s menstrual cycle. Of particular difficulty was scheduling more than 20 women to ensure that axillary odors were collected at key times during their menstrual cycles,” said first author Nozomi Ohgi, a graduate student in Touhara’s lab at the time of the study.

“We also needed to interview each participant frequently regarding body temperature and other indicators of the menstrual cycle in order to understand and track their status.”

According to Ohgi, this required a great deal of time, effort, and careful attention. “It took more than one month per participant to complete the collection within the menstrual cycle, so very time consuming.”

Body odor tests were done blindly

Another challenge the researchers faced was to ensure the tests were done “blind,” meaning the participants did not receive any hints about what they were smelling or why, with some participants being given nothing at all as a measure of control.

This way, psychological factors and expectations can be reduced or eliminated. The team also used fMRI scans to examine how male brains responded to these ovulation-related body odor compounds.

The scans showed heightened activity in the orbitofrontal cortex and fusiform gyrus. These regions process reward and facial attractiveness. The effect happened without men consciously noticing the body odor.

Still not quite pheromones

“We cannot conclusively say at this time that the compounds we found which increase during the ovulation period are human pheromones. The classical definition of pheromones is species-specific chemical substances that induce certain behavioral or physiological responses,” said Touhara.

“But from this study, we can’t conclude whether the axillary odors are species-specific. We were primarily focused on their behavioral or physiological impacts, in this case, the reduction of stress and change in impression when seeing faces. So, at this moment, we can say they may be pheromonelike compounds.”

That distinction is key. The researchers found behavioral responses, but not enough to call the compounds true pheromones. Further studies will be needed to confirm whether the effects are species-specific or consistent across diverse populations.

Future research directions

The team plans to expand their research by including a more diverse group of participants to rule out the influence of specific genetic traits.

They also aim to conduct more detailed chemical analyses to investigate how ovulatory compounds may impact brain regions involved in emotion and perception.

With more testing, these body odor compounds may offer clues about subconscious human interactions. Body odor might not change behavior dramatically, but it could quietly shape how we feel and connect.

The study is published in the journal iScience.

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