Humans can SMELL disease: Nose can detect when a person's immune system is fighting illness People can smell that the immune system has gone into overdrive within just a few hours of exposure to bacteria, the researchers claim Say different diseases also have different smells - for example, the lymph node infection scrofula is said to make the sufferer smell of stale beer People are able to smell if someone is ill, new research suggests. Scientists claim humans can smell if someone's immune system is highly active. They say people can smell that the immune system has gone into overdrive within just a few hours of exposure to bacteria. People are able to smell if someone is ill, Swedish researchers claim. They say humans can detect when a person's immune system has gone into overdrive after exposure to bacteria The researchers, at the Karolinska Institute, in Sweden, say there is even anecdotal and scientific evidence to suggest that different diseases have particular smells. For example, scrofula, an infection of the lymph nodes, is reported to smell like stale beer, and a person who suffers from diabetes is known to sometimes have breath that smells of acetone. "In this current study we have studied the ability of humans to detect disease by smell," said Professor Mats Olsson, who led the study. Being able to detect these smells would represent a critical adaptation that would allow us to avoid potentially dangerous illnesses. Humans can smell if someone's immune system is highly active because they have been exposed to bacteria. Scrofula - a lymph node infection - smells like stale beer. Diabetes makes the breath smell of acetone. The question we asked ourselves in this study was whether such an adaptation might exist already at an early stage of the disease, thereby reflecting a biomarker for illness. Professor Olsson and his team asked eight healthy people to visit their laboratory. The people were injected with either a form of lipopolysaccharide (LPS) - a toxin made from bacteria and known to ramp up an immune response - or a saline solution. The volunteers wore tight t-shirts to absorb their sweat over the course of four hours. A separate group of 40 volunteers were then asked to smell the sweat samples. Overall, they rated t-shirts from the LPS group as having a more intense and unpleasant smell than the other t-shirts. They also rated the LPS shirts as having an unhealthier smell. The researchers say different diseases smell different - for example, they say there is a lymph node infection that makes people smell of stale beer The association between immune activation and smell was accounted for, at least in part, by the level of cytokines present in the LPS-exposed blood. That is, the greater a participant's immune response, the more unpleasant their sweat smelled. "Interestingly, in a chemical assay the researchers found no difference in the overall amount of odorous compounds between the LPS and control group," said Professors Olsson. This suggests that there must have been a detectable difference in the composition of those compounds instead. While the precise chemical compounds have yet to be identified, the fact we give off some kind of aversive signal following shortly after activation of the immune system is an important finding, the researchers argue.