A new study conducted by Swedish researcher Mats Olsson of the Karolinska Institute has shown that humans may have a six sense of sorts when it comes to other people being sick. Olsson says that certain illnesses have a distinctive smell to them that some people are able to smell. One example that Olsson gives is that when someone has diabetes you can smell a faint acetone scent or rotten apple scent on their breath.
Olsson wanted to put this theory to the test so he gathered a group of researchers and eight healthy participants. Some of the participants were injected with saline while others got an injection of lipopolysaccharide (LPS). LPS is a toxin that will increase the response of the immune system. The participants were then put in tight suits that would make them sweat more and would absorb the sweat. While watching the participants in these shirts over a four hour period Olsson found that those that had been injected with the LPS had higher body temps and had higher levels of the inflammatory molecules in the body called cytokines.
Once the four hour period was over Olsson found 40 people who were willing to sniff the shirts that had absorbed the sweat of the eight participants. The people who were doing the sniffing reported a stronger smell in the shirts that turned out to be the ones who had LPS in their system. The result of the study showed that the more the immune system was working, the more unpleasant the person smelled.
Other studies have shown that no one has the same sense of smell so those who may be able to smell a sickness coming from a person may not have friends that can smell the same thing. This means that everyone experiences different smells in their own way.