Earwax Can Indicate Parkinson’s Disease, Preliminary Study Finds

In 2012, Joy Milne, a Scottish retired nurse, asked Tilo Kunath of the University of Edinburgh a surprising question during his public talk: She was curious if people with Parkinson’s disease smell different. In the time that she had spent as a nurse with Parkinson's disease patients, including her late husband, Milne had noticed a peculiar smell to be a common factor between them all.

At the time, scientists dismissed her. But seven years later, Kunath and his colleagues found a Parkinson's disease-associated signature of volatile organic compounds (VOCs) from patients’ skin—these compounds could explain the distinct smell that Milne noticed.¹ The researchers included Milne, who was later dubbed by the media as “The Woman Who Could Smell Parkinson’s”, as a co-author of the study.

Today, researchers around the world continue to look for biomarkers of Parkinson’s disease in VOCs found in the body’s secreted oily substances.² While many scientists commonly sample skin, biomedical engineer Xing Chen of Zhejiang University investigated earwax.

“This is in line with previous reports that patients with Parkinson's disease have an increased production of sebum, indicated by an oily forehead or an increased buildup of earwax,” said Drupad Trivedi, a metabolomics researcher at the University of Manchester who was not involved in the work. “Some notice that when they wake up, there are literally bits of dried earwax on their pillows.”

In a new study, published in Analytical Chemistry, Chen and his team identified four VOCs that were significantly enriched in the earwax of patients with Parkinson's Disease as compared to that of healthy people.³ Their findings suggest that these VOCs could be promising biomarkers for Parkinson’s Disease.

For their study, Chen and his colleagues collected earwax samples from 108 people with Parkinson's disease and 101 healthy people. Using gas chromatography methods, they found that four VOCs were significantly higher in earwax samples from patients with Parkinson's disease than in those from healthy people. Trivedi, who worked with Kunath on the first VOC paper, said, “I was quite encouraged to see that there are overlaps with the classes of VOCs we saw.”

“To my knowledge, this is the first time that anyone used earwax to identify Parkinson’s disease," Chen said.

Another researcher, however, was not convinced. “It’s an interesting paper, but flaws in the study’s design limit its validity,” said Richard Doty, a neuroscientist at the University of Pennsylvania who was not involved in the study. Doty said, “There’s no rationale why, physiologically, these chemicals should be involved in Parkinson’s disease.”

Doty also mentioned that many factors besides Parkinson’s disease, including age, hormones, and exposure to different environments, influence earwax constituents. Both Trivedi and Doty also noted that patients in the Parkinson's disease cohort were 20 to 30 years older than the control group. The researchers in the study corrected for this “generational” age difference using statistical approaches. “I’m not someone who is convinced with age correction based on statistics,” Trivedi said. According to him, more studies are needed to validate the researchers’ findings.

Chen acknowledged the need for further research and that his team’s results are still preliminary. “At this stage, it's quite difficult for us to conclude that this method could be used to diagnose early Parkinson’s disease,” he said.