The Smell of Sex: Women at Peak Fertility Periods Prefer Men Oozing Testosterone

Perhaps there was something in the air. Or maybe it's just that je ne sais quois, as the French say. Whatever it is, a new study shows that women may actually be able to hint the testosterone oozing off men during peak fertility periods. What does that mean, you say? The more masculine, the sexier.

According to the study, ovulation makes a strong impact on a woman's mating preference, which shows that women in the fertile phase of their menstrual cycle are more likely to dig dudes with deep voices and hair on their chests (or, rather, more testosterone...some just may not like manly looking men.) Other research also suggests that fertile women are attracted to men with high levels of the stress hormone cortisol, which may be involved in a stronger immune system.

Researchers looked at how women's sexual scent preferences varied on men's testosterone and cortisol levels. Male volunteers were given T-shirts to wear for two consecutive nights, during which they were not allowed to bathe or wear any type of colognes. They were also unable to drink or smoke or consume garlic, onion, green chilies, strong cheeses or other pungent foods, according to the study.

Then, female volunteers sniffed the men's shirts and rated the pleasantness, sexiness and intensity of the smells (on scales from 1 to 10). The women also completed a questionnaire about their stage in their menstrual cycles and whether they were using hormonal contraception.

The researchers took saliva samples from the men to measure hormone levels of testosterone and cortisol.

Women at a higher fertile stage of their cycle preferred the smell of men with higher testosterone, rating certain men's shirts as the most pleasant and sexiest. Women showed no preference to the cortisol levels.

Researchers believe this link between testosterone and attractiveness must be studied further as other studies contradict these findings.

"This is a controversial research area. Studies are highly inconsistent," said psychologist Wendy Wood of the University of Southern California, who was not involved in the study, according to LiveScience. "Only a few studies have shown that women's menstrual cycles influence their mate preferences - many more find no effects of menstrual cycles on preferences."

The chemical androstenol contributes to the musky smell of body odor. Men produce much more of this chemical than women, and testosterone levels may be linked to production of these molecules, the researchers suggest. If so, the women in the study may be responding to these subtle odor cues.

If the findings can be replicated, scientists could try to identify these odor molecules, and then figure out how they influence human scent preferences.

Whether these chemicals are signals of masculine qualities, or just a byproduct of them, remains unclear.