When Sweat is Sweet

What smells awful to one person may actually strike another as pleasant, according to a new report by Duke Medical Center researchers. The difference, they say, doesn't come down to personal preferences but to genetic variants in the odor receptors of smellers.

The researchers, led by Hiroaki Matsunami, assistant professor of molecular genetics and microbiology, focused on two chemicals—androstenone and androstadienone—that are created naturally by the body during the breakdown of the male sex hormone testosterone and are excreted in sweat and urine. The researchers sought to discover why people react differently when they smell these two chemicals.

In conjunction with collaborators at Rockefeller University, they asked 391 volunteers to inhale the two chemicals and describe what they smelled. The results ranged widely: from no smell at all to descriptions such as "vanilla and sweet" to "sickening and urine." DNA extracted from blood samples from each volunteer were sent to Matsunami's laboratory.

Humans have about 400 olfactory receptors in their noses that detect an odor, which is essentially a collection of chemicals. Smells typically bind to their corresponding receptors, which then relay information to the brain for processing.

"After performing genetic analysis on each of the samples and correlating the results with the smell descriptions, we were able to link specific genetic variants with specific perceptions," Matsunami says. "While many theories of the different perceptions of smell focus on culture, experience, or memory, our results show that an important portion of this variability is due to an individual's genes." The study was published in the journal Nature.

"These results demonstrate the first link between the functioning of a human odor receptor gene and how that odor is perceived," Matsunami says, adding that the results will likely add to the debate over the existence of pheromones in humans. Pheromones are chemical signals between animals that express alarm and provide mating and navigation cues.