Twelve years before her husband was diagnosed with Parkinson’s disease, Joy Milne noticed that he smelled different.She couldn’t explain it at the time. The smell was musky, and she assumed it was probably sweat. Years later, at a Parkinson’s support group, she walked into a room full of people with the disease and smelled it again.Milne, a Scottish nurse, eventually caught researchers’ attention. Scientist Tilo Kunath gave her T-shirts worn overnight by people with Parkinson’s and by healthy controls. She picked out all six Parkinson’s patients and also flagged one person in the control group. That person was diagnosed eight months later. “I just dismissed it, I have to say,” Kunath later told NPR. “Why should Parkinson’s have an odor?”Scientists Think Parkinson’s Could Leave a Chemical Signature on Your SkinResearchers have been chasing that question ever since. A new study in Scientific Reports took the idea somewhere most of us probably wouldn’t have guessed: the belly button.Scientists at the Fraunhofer Institute in Germany swabbed 24 people in the nose, around the ear, and inside the navel. The group included healthy people along with participants who had Parkinson’s, mild cognitive impairment, or COVID-19. The researchers then analyzed the odor compounds on those swabs using laser-based photoacoustic spectroscopy.The basic idea is much easier than the name makes it sound. Our bodies release volatile organic compounds, or VOCs, and illness can change the mix. Previous Parkinson’s research has already found changes in VOCs coming from sebum, the oily substance produced by our skin.In the new study, samples from the nose and belly button did the best job of separating the groups. Healthy participants and those with mild cognitive impairment were the easiest to tell apart. Parkinson’s and COVID-19 samples fell between them and overlapped more. A few Parkinson’s patients were tested again two weeks later, and their results stayed close to the original Parkinson’s group.This is still very early research. Twenty-four people is tiny, especially for something that could eventually be used as a medical test. Age also complicated things because the older participants naturally had different chemical profiles, and Parkinson’s and mild cognitive impairment are both more common later in life. The researchers say they’ll need a much larger group before they can tell how much of what they found comes from disease and how much comes from age.Still, Joy Milne smelled something years before doctors had a diagnosis. Now researchers are trying to figure out exactly what her nose was picking up, and apparently one place you should check is your belly button.The post Your Belly Button Could Hold a Surprising Clue to Parkinson’s Disease appeared first on VICE.