Women smell different during ovulation, men notice

When women ovulate, there are some subtle changes in the air literally.

A new study from the University of Tokyo shows that men respond to specific odor compounds that increase their odor during ovulation. These compounds not only make women smell more pleasant to their male scent, but also seem to lower male stress levels and increase the impression of attractiveness and femininity. While researchers no longer call them pheromones, evidence suggests that our noses may quietly shape social behavior in ways we don’t realize.

Three odor molecules, a powerful effect

Scientists collected and analyzed the underarm odors of 21 women during their menstrual cycle. Using gas chromatography-mass spectrometry, they identified three compounds: (E)-glycerol acetone, tetranucleic acid and (Z)-9-hexoenoic acid-reliably increased during the ovulation phase.

When they were added to baseline axillary odor and presented to male subjects, the results were obvious:

• Men rate the smell as more pleasant
• Related female faces are considered more attractive and feminine
• Men report feeling more relaxed
• Amylase’s saliva levels are biomarkers of stress, reducing

“These results suggest that body odor may help communication between men and women,” said Professor Kazushige Touhara, senior author of the study.

Not very informative, but still valid

Although these findings echo the effects of pheromones similar to animals, researchers are cautious not to claim that they have found human pheromones. “At the moment, we can’t finally say that the compounds we found… are human pheromones,” Touhara explained. “But… they may be pheromone compounds.”

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

Smell and Attraction: Subconscious Signal?

Past research suggests that it is more pleasant for men to find female odor near ovulation, but this is the first chemically isolated compounds responsible for this transition. The team’s double-blind design ensures that men don’t know their scent or why suggestive cues are ruled out. The emotional impact is not only on men’s heads: even their physiological stress marks have changed.

The researchers also found that these scents changed how men perceive female faces. Attractive faces become more attractive when paired with ovulation-related scents. However, the faces with high ratings remain consistent – the odor emitted may give some women a subtle advantage in the peak fertility process.

Evolutionary echoes in modern context

In other mammals, ovulating body odors often act as direct signals for mating. In humans, this influence may have evolved into something more gentle and indirect, a way to influence emotions and perceptions rather than direct contact with the behavior.

“The role of ovulation odor may have shifted… from pheromones that release classical behaviors to communication tools that positively affect emotions,” the author writes.

Interestingly, these three compounds have links to other biological fluids. Tetranucleic acids are found in breast milk and amniotic fluid. (e) – Glycylone gives off a green floral scent. (Z)-9-hexadienoic acid is related to skin lipid metabolism. Together, they may form part of the original sensory vocabulary that connects humans under the surface.

What’s next?

The researchers plan to expand the study to different populations and genetic backgrounds. Future work may also track brain activity for these odors, or study whether similar signals exist in male body odors.

Currently, research shows that even in our modern, rational society, instinct can still find a way to whisper in the nose.

Magazine: Iscience (Published on July 28, 2025)

doi: 10.1016/j.isci.2025.113087

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