Do women smell more attractive to men during their fertile days? Several previous studies had answered this question with a yes. However, a new study has come to the opposite conclusion. Chemical analyses of women’s armpit sweat showed no change over the course of the cycle. Male test subjects also did not rate the body odor of fertile women as more attractive. The research team explains the discrepancy with previous results by saying that the current study used a more rigorous methodology.
In the animal kingdom, females of many species clearly signal when they are ready to mate and fertile – either through visual or olfactory cues. Some studies have also suggested that men find women’s body odor more attractive in the days around ovulation. However, many of these studies had methodological flaws. It was also unclear which of the chemical compounds emitted by women could be responsible for making them appear more attractive in certain phases of the cycle.
Armpit sweat for science
A team led by Madita Zetzsche from the University of Leipzig has now used two different methodological approaches to investigate whether the fertile days of human women can actually be sniffed out. “We combined perception and chemical analyses to examine the armpit odor of women during the ovulation cycle,” the team reports. Only heterosexual participants with a natural cycle who did not smoke or eat meat during the time around their participation in the study were included, as these factors can influence body odor.
For the study, the 29 women who took part stuck cotton pads under their armpits on ten evenings and delivered the odor samples to the laboratory the next morning. The test dates were distributed so that samples were collected before, during and after ovulation, with a focus on the fertile days. The researchers also collected air samples from the armpit area of 16 participants in order to chemically analyze them. Using urine and saliva samples, they recorded which phase of the cycle the respective odor donor was in and how high her level of the hormones estrogen and progesterone was.
No more attractive fertility smell
For the perception test, the team asked 91 heterosexual men to sniff the cotton pads and indicate how intense, pleasant and attractive they found each smell. “Our results showed no indication that female fertility makes women’s body odor more attractive to men,” the team writes. On the contrary: “Contrary to our expectations, men found the armpit odor of women in the fertile phase less pleasant and less attractive.” Statistical robustness analyses, however, showed that these negative results are not consistent. They therefore do not allow the conclusion that women smell less attractive during ovulation.
The chemical analyses confirmed the results of the perception study. “In our analysis, we found no convincing evidence that changes in female fertility are associated with chemical variations in the composition of women’s armpit odor,” write Zetzsche and her team.
Discrepancy with previous studies
The researchers assume that the contradictory results of earlier studies are based on methodological weaknesses – for example, that the cycle phase was not verified hormonally or that the male test subjects evaluated several samples of the same odor donor. “We now have more robust methods at our disposal. It is therefore possible that newer and methodologically more rigorous studies come to different results than those from ten years ago,” explains Zetzsche.
The researchers suggest checking the results in further methodologically high-quality studies to find out whether the deviation in earlier studies was actually only due to methodological reasons, or whether it indicates biological effects that have not been taken into account so far. “We hope that this study will inspire further research that looks more closely at the chemical component of body odor,” says Zetzsche’s colleague Anja Widding. “In some non-human primates, my team and I were able to demonstrate a connection between body odor and fertility. In this respect, we are very interested in how this phenomenon developed in human evolution.”
Source: Madita Zetzsche (University of Leipzig) et al., Proceedings of the Royal Society B – Biology Letters, doi: 10.1098/rspb.2023.2712