A chance encounter more than a decade ago has opened the door to a new frontier in medical diagnosis: using smell to detect diseases years before symptoms appear.
In 2012, retired Scottish nurse Joy Milne told researchers she could identify Parkinson’s disease by scent alone. Her unusual claim was initially dismissed as implausible. But when scientists at the University of Edinburgh put her to the test, Milne correctly distinguished Parkinson’s patients from healthy individuals simply by sniffing T-shirts they had worn. In one striking case, she identified a person as having the disease months before a formal diagnosis.
The discovery confirmed that Parkinson’s produces a distinct musky odour — and that Milne, who has an inherited condition called hyperosmia that heightens her sense of smell, could detect it. Her story made headlines in 2015 and has since inspired a wave of scientific research into the hidden world of human scent.
Scientists now know that the body continuously releases volatile organic compounds (VOCs) through sweat, breath, and urine. These chemical signatures change when disease alters normal metabolism. “Having a disease can change your body’s odour fingerprint,” explained Bruce Kimball, a chemical ecologist at the Monell Chemical Senses Center in Philadelphia.
Researchers are now working to harness these odour cues for medical testing. In Manchester, chemist Perdita Barran is developing a simple skin swab that could detect Parkinson’s before tremors and other symptoms emerge. Using advanced techniques such as gas chromatography-mass spectrometry, her team has identified a cluster of lipids consistently altered in patients, providing a biochemical explanation for the musky smell Milne noticed years earlier.
The potential extends far beyond Parkinson’s. Distinct smells have long been linked to illnesses: diabetics in crisis may smell fruity due to ketone build-up, while liver or kidney disease can cause musty or ammonia-like odours. Certain infections, such as cholera or tuberculosis, also give off tell-tale scents.
Dogs, with their highly sensitive noses, have been trained to detect cancers, malaria, and even impending epileptic seizures. In one study, dogs identified prostate cancer in urine samples with 99% accuracy. However, training animals on a large scale is impractical. Companies such as RealNose.ai are now developing “electronic noses” to replicate canine abilities and turn scent-based diagnostics into reliable, non-invasive tests.
For Milne, whose husband Les was diagnosed with Parkinson’s before her discovery, the research is bittersweet. But her story has sparked global interest in a field that could revolutionise healthcare.
“We’re on the brink of creating fast, non-invasive diagnostics,” Barran said. “The signals are already there, right under our noses.”
