It may be possible to "sniff out" sickness, according to a new study.
The research, published in the journal Psychological Science, shows that it's possible to detect differences in odor that occur from a body's increased immune response.
For the study, researchers from the Karolinska Institutet in Sweden had eight healthy people receive injections of either a saline solution (the control group), or injections of a toxin that is known to increase the body's immune response (it caused the participants to have a higher body temperature, and also increased the immune response by upping levels of cytokines). The researchers had the participants wear tight shirts to absorb their sweat for four hours.
Then, 40 separate study participants were asked to sniff the sweaty shirts of the people who received the toxin or saline injections. They were asked to describe any differences in smell.
The shirts that were worn by the people injected with the toxin were described as having an "unhealthier," more unpleasant, and more intense smell, than the shirts worn by the people injected with the saline.
When researchers looked at the actual number of odorous compounds in the sweaty shirts of the toxin-injected people and the saline-injected people, they found no differences, which suggests that the differences in odor may instead be from the composition of the compounds, versus the number of compounds.
The findings suggest "there may be early, possibly generic, biomarkers for illness in the form of volatile substances coming from the body,” study researcher Mats Olsson said in a statement.