Women Smell Different During Ovulation, and Men Notice

When women ovulate, something subtle shifts in the air, literally.

A new study from the University of Tokyo reveals that men react measurably to specific scent compounds that increase in female body odor during ovulation. These compounds don’t just make women smell more pleasant to men, they also appear to lower male stress levels and boost impressions of attractiveness and femininity. While researchers stop short of calling them pheromones, the evidence suggests our noses may quietly shape social behavior in ways we don’t consciously detect.

Three Scent Molecules, One Powerful Effect

Scientists collected and analyzed underarm odors from 21 women across their menstrual cycles. Using gas chromatography-mass spectrometry, they identified three compounds—(E)-geranylacetone, tetradecanoic acid, and (Z)-9-hexadecenoic acid—that reliably increased during the ovulatory phase.

When these were added to a baseline armpit odor and presented to male subjects, the results were clear:

• Men rated the scent as significantly more pleasant
• Associated female faces were judged more attractive and feminine
• Men reported feeling more relaxed
• Salivary levels of amylase, a biomarker for stress, decreased

“These results suggest that body odor may in some way contribute to communication between men and women,” said Professor Kazushige Touhara, the study’s senior author.

Not Quite Pheromones, but Still Potent

Though the findings echo pheromone-like effects seen in animals, the researchers are careful not to claim they’ve found human pheromones. “We cannot conclusively say at this time that the compounds we found… are human pheromones,” Touhara explained. “But… they may be pheromonelike compounds.”

This distinction matters. True pheromones must produce consistent, species-specific responses. Human scent, on the other hand, is complex and filtered through layers of psychology, culture, and individual variation.

Smell and Attraction: A Subconscious Signal?

Past studies hinted that men find female scent more pleasant near ovulation, but this is the first to chemically isolate compounds responsible for that shift. The team’s double-blind design ensured men had no idea what they were smelling or why, ruling out suggestive cues. And the emotional effects weren’t just in men’s heads: even their physiological stress markers changed.

The researchers also found that these scents altered men’s perceptions of female faces. Less-attractive faces became more appealing when paired with ovulation-associated odors. High-rated faces, however, stayed consistent—suggesting scent may give some women a subtle edge during peak fertility.

Evolutionary Echoes in Modern Contexts

In other mammals, ovulatory body odors often act as direct signals for mating. In humans, such effects may have evolved into something more muted and indirect—a way of influencing mood and perception rather than triggering behavior outright.

“The role of ovulatory odors might have shifted… from the classical behavior-releasing pheromone to a communicative tool that positively affects emotions,” the authors write.

Interestingly, the three compounds have connections to other biological fluids. Tetradecanoic acid is found in breast milk and amniotic fluid. (E)-geranylacetone emits a green, floral scent. And (Z)-9-hexadecenoic acid is linked to skin lipid metabolism. Together, they may form part of a primal sensory vocabulary that shapes human connection beneath the surface.

What Comes Next?

The researchers plan to expand the study across different populations and genetic backgrounds. Future work may also track brain activity in response to these scents or investigate whether similar signals exist in male body odor.

For now, the study suggests that even in our modern, rational society, instinct still finds a way to whisper through the nose.

Journal: iScience (published July 28, 2025)

DOI: 10.1016/j.isci.2025.113087

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