Armpit Sniffing Study Reveals That the Most Fertile Women Smell Best to Men

Scent is thought to play an import role in who we find attractive. In fact, it is widely believed among experts that everyone has their own distinctive body odor, which an individual may find either off-putting or appealing.

However, many aspects of scent's role in attraction remain unclear, such as whether certain women smell more attractive to men than others and if so, why this is the case.

Now, a team led by researchers from the University of Bern, Switzerland, has found that a woman's body odor (BO) is linked to her levels of reproductive hormones, and that men generally agree on who smells the most attractive, according to a study published in the journal Proceedings of the Royal Society B.

Related research on the physical attractiveness of women's faces and bodies has shown that men display remarkable agreement on who they consider to be attractive or not attractive.

Evolutionary theories of attractiveness suggest that men should prefer women who show signs of high reproductive health and fertility—a state that's linked to high levels of reproductive hormones which increase the chance of conception.

Female hormones, such as oestradiol and progesterone, have been linked to women's facial and body attractiveness. For example, higher levels of these two substances lead to larger breasts and curvier waists resulting in the hourglass figure that, according to research, men typically prefer.

The latest study explores, for the first time, whether a similar situation exists when it comes to body odor: one where scent acts as a "marker" of reproductive fitness, in the same way that physical features are an indicator.

"Smelling another person's body odour can be a poignant and sexually arousing experience, or it can be rather unpleasant and off-putting," Janek Lobmaier, an author of the study from Bern's Institute of Psychology, told Newsweek. "This has lead some scholars to suggest that olfaction is even more important when choosing a mate than for example visual attractiveness. But compared to studies on for example facial and body attractiveness, the literature on the role of body odor in human mate preferences is scarce."

The team investigated differences in the body odors of women to find out whether some individuals generally smell more attractive than others to men, or if odor preference is simply a matter of individual taste—and whether levels of reproductive hormones explain women's body odor attractiveness.

To do this, the scientists conducted a rather unusual experiement in which they asked 57 lucky male participants to smell body odor samples taken from the armpits of 28 different women of reproductive age. The BO samples were collected at peak fertility—when women can conceive—to control for the effects of the menstrual cycle on odor attractiveness.

They found that—just like physical preferences—men largely agreed on which odors were more attractive. Furthermore, they found that the higher a woman's level of oestradiol and the lower her levels of progesterone, the more attractive her odor was rated.

Stock image of a woman showing her armpit. iStock

This negative relation between women's progesterone levels and BO attractiveness may seem surprising because, as previously noted, the hormone is related to a woman's reproductive potential.

However, this finding can be explained by the fact that the odors were collected at peak fertility, when women have high levels of oestradiol and low progesterone levels. Essentially, the men rated the odors from the most fertile women—those with the highest oestradiol and lowest progesterone levels—as the most attractive.

"The most surprising result was the degree to which men agreed on which body odours they found attractive," Lobmaier said. "This suggests that body odour attractiveness does not lie in 'the nose of the smeller'. The fact that levels of reproductive hormones explained body odour attractiveness of women is interesting and fits very well with evolutionary explanations, since women with high oestradiol levels are potentially more fertile than women with less oestradiol—and hence, following an evolutionary approach to attractiveness, should be more attractive."

These results suggest that body odor acts as a cue to potential fertility, according to the researchers: the higher a woman's fertility, the more attractive her body odor is to men.

"Within an evolutionary framework, these findings are meaningful and interesting: an evolutionary approach to female attractiveness proposes that men should generally prefer women who signal high reproductive health and fertility," Lobmaier said.

There has been much debate among scientists in recent times on whether preferences of body odor are based on genetics. This hypothesis states that if two people are a good genetic match, they will find each other's smell appealing. However, the researchers in the latest study controlled for certain genetic influences and found that they played no significant role in how men rated the body odors of women.

This article was updated with comment from Janek Lobmaier.