Notice that your partner’s breath smells funny? Or that their body is giving off an unusually unpleasant odor? That may be your nose alerting you to the fact that they’re sick.

According to a new study published out of Sweden, one of the first disease detectors is the human nose, which was shown in their research to pick out toxins even at the early stage of illness.

The research stems from anecdotal evidence of certain diseases carrying specific smells. People with diabetes, for instance, can have breath that smells like rotten apples or acetone.

To put their hypothesis to the test, scientists from the Karolinska Institutet injected eight individuals with either a saline solution, or lipopolysaccharide (LPS), a toxin known to activate the immune response.

The volunteers were then instructed to wear tight T-shirts for four hours, to absorb sweat.

Those injected with LPS experienced elevated body temperatures and increased levels of a group of immune system molecules known as cytokines.

Another group of 40 participants was recruited to smell and evaluate the sweat samples. Overall, T-shirts from the LPS group were rated as more intense and unhealthy (i.e., unpleasant) than the other samples.

It’s a similar concept used by scientists at the University of Huddersfield, who are working on a breathalyzer device that will be able to detect early signs of lung cancer with a breath test.

The aim is to catch cancer at the early stages with the help of a simple, non-invasive procedure.

The study was published online in Psychological Science.