WASHINGTON, January 25, 2014—A Swedish study published Thursday suggests that humans may be able to smell the body’s immune response to illness in the sweat of individuals who are sick just hours after infection.
“There may be early, possibly generic, biomarkers for illness in the form of volatile substances coming from the body,” explains study researcher Mats Olsson of the Karolinska Institutet in Sweden.
Published in the journal Psychological Science, the team conducting the study divided eight healthy people into two groups. One group was injected with lipopolysaccharide (LPS), a toxin that ramps up the body’s immune response. The other group was injected with a saline solution that was not expected to have any effect on the subjects.
Members of both groups then wore tight fitting t-shirts that would absorb their sweat for four hours. Subsequently, a separate group of 40 participants were asked to smell sweat samples taken from the t-shirts worn by the two groups.
According to researchers, overall, participants rated the samples from the LPS group as having a more unpleasant and intense odor than the control group samples. Participants also rated the LPS group shirts as having an unhealthier smell.
Study authors note that the subjects injected with LPS exhibited a perceptible immune response with elevated body temperatures and increased levels of cytokines, a group of molecules that aid in the body’s immune responses.
The study concludes that the difference in smell can be at least partially explained by an association between immune response and cytokine levels in the LPS-exposed blood, “the greater a participant’s immune response, the more unpleasant their sweat smelled,” stated the authors in a press release.
The notion that humans may be able to smell the body’s immune response to disease is not new. Some say that certain diseases have a particular smell. For example, the breath of people suffering from diabetes reportedly smells like rotting apples or acetone.
The same may be true for sexually transmitted diseases. In a 2011 study published in the Journal of Sexual Medicine, Russian researchers found that subjects rated the sweat from men with gonorrhea as more unpleasant than the sweat of those without the disease.
“While the precise chemical compounds have yet to be identified, the fact we give off some kind of aversive signal shortly after the immune system has been activated is an important finding,” said the researchers. “It grants us a better understanding of the social cues of sickness, and might also open up doors for understanding how infectious diseases can be contained.”