By all appearances, the study looked like a standard chemistry and psychology mashup: collect armpit sweat, identify the molecules, run blind tests on unsuspecting volunteers. But what it uncovered was something weirder, deeper — and a bit more primal.
At the University of Tokyo, a team of biochemists and neurointelligence researchers set out to answer a question that has long hovered in the background of perfume ads and dating advice: Can human body odor actually affect someone’s mood or perception?
Their answer isn’t a bold “yes,” but it’s not a “no” either. In fact, it’s a deeply fascinating “something is going on here.”
“We identified three body odor components that increased during women’s ovulatory periods,” said study co-author Kazushige Touhara. “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.”
Put simply, something in the scent of ovulating women seems to make men chill out — and find faces cuter.
Welcome to the Scent Lab
This wasn’t a casual nose-based vibe check. The researchers gathered 84 body odor samples from 21 women across their menstrual cycles, using medical gauze and a polymer membrane that clings to scent molecules like lint to a hoodie. Participants were monitored for body temperature, hormone levels, and ovulation timing.
Then came the male raters. These volunteers were handed the scent samples under blind conditions (meaning they had no clue where or when the odors came from). They had to rate intensity, pleasantness, emotional impact, and how they felt about some female faces while sniffing.
Out of 98 different scent compounds identified across the menstrual cycle, three stood out during ovulation:
- (E)-geranylacetone, a floral-ish aldehyde
- Tetradecanoic acid, a fatty acid found in breast milk and skin
- (Z)-9-hexadecenoic acid, a nearly scentless fatty acid with a biochemical résumé tied to aging
When this trio mixed together and added to a background “model” armpit odor, men judged the result as more pleasant and more feminine. Faces rated under the influence of these ovulation-linked compounds also got a glow-up in the men’s minds — especially faces previously considered average.
Even more compelling? Saliva samples showed these scents lowered levels of alpha-amylase, a stress biomarker.
“Furthermore, those compounds were found to relax the male subjects… and even suppressed the increase in the amount of amylase (a stress biomarker) in their saliva,” Touhara added.
In other words: something in the ovulation odor mix is dampening stress responses in men and dialing up their sense of attraction. Whether that’s evolution whispering through skin molecules, or a cultural loop feeding back into biology, is still up for debate.
Are These Human Pheromones?
Let’s pause here. It’s tempting to yell “PHEROMONES!” and sprint to the nearest frisky nightclub armed with a cotton swab. But the researchers are careful not to claim that.
Pheromones, as defined in the animal world, are chemical messengers that drive hardwired behavior — think ants following invisible scent highways or hamsters getting instantly aroused from a single whiff.
Humans, by contrast, are a bit more complicated. We’re culturally overclocked and often self-aware enough to ignore our instincts (or monetize them). So, while these odor compounds do seem to influence mood and perception, calling them pheromones may be premature. So far, no conclusive evidence of human sex pheromones has been shown in the scientific literature.
“We cannot conclusively say at this time that the compounds we found . . . are human pheromones,” Touhara said. “We were primarily focused on their behavioral or physiological impacts… So, at this moment, we can say they may be pheromonelike compounds.”
Evolution or Social Engineering?
The real kicker here is what this says about how humans possibly evolved to communicate, court, or connect without even noticing. In many mammals, scent is everything — when to mate, who to mate with, whether a rival is nearby.
Humans might not have an instinctive reaction to another’s body odor, but this study suggests that, under certain conditions, our perceptions are slightly modified. It’s not an uncontrollable command, but more like a nudge.
And we may already be responding to it, without realizing.
Other studies have shown that ovulation affects voice pitch and even facial appearance. What this research adds is a possible scent-based layer. That olfactory cue might be part of an unconscious package deal. What’s interesting is that faces rated under the influence of ovulation scents were judged more attractive — but only if they started out as average.
High-attractiveness faces didn’t change much. Which raises a whole new set of questions. Are we using scent as a kind of evolutionary equalizer? A low-key boost for folks who don’t already dominate the mating game?
Touhara’s team stops short of answering.
The Limits of the Nose
Before we start bottling armpit chemistry and rebranding it as cologne, it’s important to recognize the limits here.
The study’s participants were all Japanese, and cultural context matters. What smells “pleasant” to one group might read as sour milk to another. Genetic variation also plays a role in how people perceive scent, with known differences in olfactory receptors across populations.
The researchers acknowledge this.
“By conducting sensory evaluations and chemical analysis of axillary odor across diverse ethnic groups . . . it should be possible to perform a detailed investigation,” they write.
They’re also cautious about the hype. The study was exploratory and didn’t correct for multiple testing comparisons — meaning there’s a higher chance of false positives. Still, the findings are compelling enough to fuel future studies, especially into how the brain processes these compounds.
Touhara’s team is already planning to track how ovulation odors affect activity in brain areas tied to emotion and social perception.
The findings appeared in the journal iScience.
