Smelling a compound in men’s sweat called androstadienone raises levels of the hormone cortisol in heterosexual women, a small study has found, suggesting for the first time that human pheromones might be useful in clinical medicine.

Smelling androstadienone has previously been shown to improve mood and increase sexual arousal in women, but this is the first time that an olfactory stimulus from a specific molecule has been found to lead to a change in hormone levels. The study appears in the Feb. 7 issue of The Journal of Neuroscience.

Researchers gave 21 women 20 sniffs from a bottle containing 30 milligrams of androstadienone, and then, on a different day, had them sniff an identical bottle that contained baker’s yeast, a similar-smelling substance. Neither the researchers nor the subjects knew which bottle was being presented.

The researchers then took saliva samples to track changes in levels of cortisol, a hormone that increases blood pressure and blood sugar levels, among other effects. Sniffing androstadienone significantly improved the women’s mood and increased their sexual arousal, according to the women’s own descriptions, and raised their cortisol levels as measured by saliva tests.

The authors acknowledge that they cannot unequivocally determine whether androstadienone influenced cortisol, which then influenced mood, or whether a change in mood caused by another mechanism led to a change in cortisol.

“Manipulating hormones is a route for therapy in many diseases,” said Noam Sobel, the senior author and now associate professor of neurobiology at the Weizmann Institute in Israel. “Usually, altering hormones has lots of unpleasant side effects. If we can trigger hormone changes by smell, fool the system into changing levels of hormones, that can be really powerful.”