21 WOMEN SNIFFED A MALE SWEAT CHEMICAL, AND CORTISOL ROSE

Women who simply sniffed a male sweat compound kept higher levels of the hormone cortisol, a study found.

Researchers Claire Wyart, Wallace W. Webster, J. H. Chen, S. R. Wilson, A. McClary, R. M. Khan and Noam Sobel published the results in the Journal of Neuroscience on February 7, 2007. The main experiment involved 21 heterosexual women and a chemical called androstadienone.

“We found that merely smelling androstadienone maintained significantly higher levels of the hormone cortisol in women,” the study authors wrote in the abstract.

The paper describes androstadienone as present in male sweat and other male secretions. It also occurs in male saliva and semen.

How the test worked

Each woman came in twice and smelled androstadienone one day and a control substance on the other. The control was baking yeast, chosen and adjusted to match the compound’s smell intensity and pleasantness.

The design was double-blind. Neither the participants nor the experimenters knew which substance was in play. Women took a set number of timed sniffs in each session, and the sessions ran one week apart at the same time of day.

Participants reported good general health and no chronic medication. They had no history of anosmia or nasal injury, and none used oral contraceptives. The testing took place in an odor-controlled room with temperature and humidity control, HEPA and carbon filtration, and stainless-steel-coated surfaces.

The researchers measured cortisol in saliva. They picked it because it is associated with arousal and mood.

What the numbers showed

Cortisol levels were similar between the two conditions at baseline. After exposure, they were significantly higher in the androstadienone condition than in the control condition.

Cortisol generally dropped as the sessions went on, but it fell less after androstadienone. The authors said the effect showed up within 15 minutes and lasted as long as 60 minutes after exposure.

“Smelling pure AND had a repeatable effect on levels of cortisol,” the authors wrote in the discussion section.

The team also ran a replication with additional participants, with sessions 28 days apart to address possible menstrual-cycle effects. The paper reported nearly identical results.

Women also gave higher positive-mood ratings and reported more subjective sexual arousal after androstadienone than after the control. A composite autonomic-arousal score was higher too.

The caveats the authors flagged

The researchers did not claim to know which way the effect ran. “We cannot unequivocally determine whether AND influenced cortisol, which then influenced mood, or in turn, whether AND influenced mood through some nonhormonal mechanism, and the change in mood then led to a change in cortisol,” they wrote in the paper, available through PubMed Central.

They also did not call androstadienone a proven human pheromone. They described human pheromones as an open scientific question and the compound as a putative chemosignal.

The study identified one sweat component that can affect cortisol. The authors noted it does not establish that this is the only sweat constituent capable of influencing endocrine responses.

The work built on earlier research that reported menstrual-cycle alterations after exposure to human sweat. Other earlier work found changes in women’s luteinizing-hormone secretion and mood after exposure to male underarm extracts. Those studies never identified the specific molecules responsible.

What the authors proposed

The researchers looked ahead to possible uses. “We suggest that human chemosignals present a novel and more natural mechanism of endocrine therapy,” they wrote in the discussion section.

That was a proposal, not a result. The study did not demonstrate a treatment or clinical benefit, and purified or synthetic chemosignals remain a suggested application rather than an established therapy.