Humans Can Smell Sickness, Researchers Find

Humans have the ability to smell an illness in a person, according to researchers from Sweden.

Studies have shown that dogs and even fruit flies can smell cancers. But, can humans smell diseases too?

According to Mats Olsson of Karolinska Institutet in Sweden, there is both anecdotal and scientific proof showing that diseases have specific smells.

Rob Dunn, a science writer and biologist in the Department of Biology at North Carolina State University had recently written in a blog that humans prefer the smell of healthy humans over unhealthy ones. Dunn isn't part of the current study.

Being able to smell people who have certain diseases might be an evolutionary trait that helps humans avoid the illness. "There may be early, possibly generic, biomarkers for illness in the form of volatile substances coming from the body," said Olsson in a news release.

In the present study, researchers injected eight people with either lipopolysaccharide (LPS) - a toxin that increases immune response or a saline solution (control). The participants were then given tight t-shirts that absorbed sweat over the next four hours.

Participants injected with the toxin had a higher body temperature and cytokines- molecules linked with immune response.

Next, a group of 40 participants was asked to smell shirts containing sweat from LPS and the control group. A majority of the participants rated the LPS shirt unpleasant and unhealthier than the control group shirt.

Researchers found there was a correlation between cytokine-level in the participants' blood and unpleasant smell; higher the levels of cytokines, higher the rating on the bad odor scale.

Surprisingly, researchers conducted chemical assays and found no difference in odorous compounds in the sweat samples.

The study is published in the journal Psychological Science.