Changes in female body odor during ovulation trigger measurable reactions in men

Researchers at the University of Tokyo have studied how female body odor can influence male behavior. They found that certain aromatic compounds in female body odor increase during ovulation and can subtly influence male perception.

When these compounds were added to armpit odor samples, men rated them as more pleasant and the faces associated with these odors as more attractive. They also reported a reduction in stress levels. The scientists emphasize that this is not yet proof of the existence of pheromones in humans, but the sense of smell may subtly shape the ways in which people interact.

Although pheromones are often mentioned in pop culture, especially romantic comedies, and are thought to be substances that alter behavior between organisms, they have not yet been definitively proven to work in humans. However, a new study from the Department of Applied Biochemistry and the Worldwide Research Center for Neurointelligence (WPI-IRCN) at the University of Tokyo shows that something measurable and interesting is going on – something similar to the concept of pheromones.

"We identified three components of body odor that increase in concentration during ovulation in women. When men inhaled a mixture of these compounds and a model odor from their armpits, they rated the samples as less unpleasant and the images of women as more attractive and feminine," says Professor Kazushige Touhara.

"In addition, these compounds caused relaxation in men compared to the control group and even suppressed the increase in amylase (a biomarker of stress) in saliva. These results suggest that body odor may somehow facilitate communication between men and women."

Previous studies have shown that women's body odor changes throughout the menstrual cycle, and that changes during the ovulation phase can be perceived as pleasant by men. But the specific components of these odors have not yet been identified—a problem that the new study addresses. To do this, Tohara's team used gas chromatography-mass spectrometry to identify volatile compounds that change during different phases of the cycle.

"The most challenging part was determining the armpit odor profile during a woman's menstrual cycle. It was especially difficult to organize the schedule of more than 20 women to collect odors at key points in their cycle," says first author Nozomi Ohgi, a former graduate student in Tohara's lab.

"We also had to frequently ask each participant about their body temperature and other menstrual cycle parameters to track their progress. This required a lot of time, effort and attention. It took more than a month for one participant to complete the data collection for one cycle, so it was very labor-intensive."

Another challenge was to conduct “blind” tests: the participants did not know what exactly they were inhaling and for what purpose. Some did not receive any smells at all – as a control. This was necessary to exclude psychological attitudes and expectations.

However, beyond the experiment, another question remains: will the nature of this study lead people to rush to regard it as evidence of the existence of pheromones in humans, as happens in some animals, including mammals.

"We cannot yet state unequivocally that the compounds we discovered, the concentration of which increases during ovulation, are human pheromones. The classic definition of pheromones is species-specific chemicals that cause certain behavioral or physiological reactions," emphasizes Professor Tohara.

"But we can't conclude from this study whether armpit odors are species-specific. We were primarily interested in their behavioral or physiological effects — in this case, stress reduction and changes in the perception of faces. So at this point, we can say that they may be pheromone-like compounds."

The team plans to continue their work, including expanding the study population (to rule out genetic influences), conducting more in-depth chemical analysis, and investigating how ovulatory compounds influence activity in brain regions associated with emotion and perception.

The study is published in the journal iScience.