Women’s armpit BO can sometimes be relaxing for men

It’s not just love in the air.

In a shocking new study out of Japan, scientists had men smell women’s armpits — and discovered that their body odor could subtly sway male behavior, even helping them relax.

But the effect only kicked in at certain times of the month, when the men found the scent more appealing — and the women’s faces suddenly looked a whole lot cuter to the guys doing the sniffing.

Armpit alchemy

Previous research has shown that women’s body odor changes throughout the menstrual cycle, with men often finding it more appealing around ovulation, when fertility peaks.

But the chemical cocktail responsible for turning sweat into a subtle signal has remained a mystery, until now. 

Using high-tech chemical analysis, researchers at the University of Tokyo pinpointed three body odor compounds that fluctuate throughout the menstrual cycle and spike during ovulation. 

When those compounds were added to armpit sweat samples taken from women, men consistently rated the scent as more pleasing and the matching faces as more attractive and feminine.

Fascinatingly, getting a whiff of those compounds also appeared to relax the male participants, reducing levels of a stress biomarker in their saliva compared to a control group.

“These results suggest that body odor may in some way contribute to communication between men and women,” Dr. Kazushige Touhara, a professor in the Department of Applied Biological Chemistry at the University of Tokyo, who helped lead the study, said in a statement.

Sniffing out the truth on human pheromones

Pheromones — often called “love chemicals” — are a well-documented part of the animal kingdom. Bugs, birds and beasts use these scent signals to send subtle messages to other members of the same species about things like mating, social bonding and territorial marking.

And while Hollywood loves the idea of invisible aromas sparking instant lust, real-world scientists aren’t convinced it works the same way for humans.

Some small studies have suggested that certain compounds — like androstadienone from male sweat and estratetraenol from female urine — might affect mood and attraction.

But those findings have been called into question due to methodological issues, like participant hygiene and inconsistent odor detection.

In the Japanese study, nailing down the right chemical mix was anything but easy.

“Of particular difficulty was scheduling more than 20 women to ensure that axillary [armpit] 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,” she added, noting that each subject took more than a month to fully monitor and sample.

Even with all that careful planning, Touhara wasn’t ready to declare the compounds true human pheromones.

“We cannot conclusively say at this time that the compounds we found which increase during the ovulation period are human pheromones,” he said.

One lingering question: Are the armpit scents identified in the study “species-specific” — a defining feature of pheromones in the animal world?

“At this moment, we can say they may be pheromone-like compounds,” Touhara said.

Looking ahead, the team hopes to build on their research by including a more diverse pool of participants to eliminate the chance of specific genetic traits influencing results. 

They’re also aiming to dig deeper into the brain’s response to these compounds, particularly the regions tied to emotion and perception.