Our bodies constantly emit chemical compounds through our skin and breath—many of which may indicate illness long before symptoms appear. Scientists are now turning to these subtle scents as powerful diagnostic tools.
One of the most astonishing cases emerged in 2012, when Joy Milne, a retired nurse from Scotland, told neuroscientist Tilo Kunath that she could smell Parkinson’s disease. Initially skeptical, Kunath and analytical chemist Perdita Barran decided to put her claim to the test. Milne identified Parkinson’s patients from T-shirts worn by volunteers—correctly spotting all six known cases and even one undiagnosed person, who was confirmed with the disease a year later.
It was the beginning of a groundbreaking scientific effort. Milne, it turned out, had hereditary hyperosmia, an unusually heightened sense of smell, allowing her to detect biochemical changes that most people miss.
The Science of Disease-Linked Scents
Human bodies release volatile organic compounds (VOCs)—small, airborne molecules that result from our metabolism. When disease alters our internal chemistry, it also changes the VOCs we emit. These changes can produce noticeable smells. For example:
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Diabetes can give breath a fruity smell due to ketone buildup.
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Liver disease may cause a musty or sulphurous odour.
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Kidney issues may result in breath smelling like ammonia or fish.
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Tuberculosis has been linked to a stale beer scent.
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Malaria can make infected children emit a fruity-grassy scent that attracts mosquitoes.
Even some cancers and neurological conditions, including Parkinson’s disease, release distinct VOC profiles—though these changes are usually too subtle for most human noses.
Turning Noses Into Tools
Dogs, with their extraordinary olfactory sensitivity, have already been trained to sniff out various diseases—cancers, Parkinson’s, diabetes, and even seizures—with impressive accuracy. But training dogs is time-consuming, and not all animals are suited to the task.
Now, researchers are aiming to replicate this natural detection system with machines. Scientists like Barran are using gas chromatography-mass spectrometry (GC-MS) to analyze skin oils (sebum) and isolate specific molecules tied to Parkinson’s. Her team has narrowed down a list of about 30 consistent compounds—mainly lipids and fatty acids—that appear to be markers for the disease.
The goal is to develop non-invasive diagnostic tools, such as a simple skin swab test that could detect Parkinson’s before physical symptoms appear. This would be a major improvement over current methods, which often take years for a formal diagnosis.
Expanding the Scent-Based Frontier
In the U.S., scientist Bruce Kimball is working on VOC-based diagnostics for brain injuries and infections. His research shows that many diseases have distinct chemical signatures, even shortly after injury or infection.
Meanwhile, RealNose.ai, co-founded by physicist Andreas Mershin, is developing a “robotic nose” using real human olfactory receptors and AI. This synthetic system mimics how a brain processes smells and is being trained to recognize scent patterns linked to diseases like prostate cancer.
Joy Milne’s Lasting Impact
Now in her 70s, Milne continues to support the research as part of Barran’s team. Though she no longer routinely performs scent tests—both due to the emotional strain and her age—her unique gift helped launch a new frontier in medical science.
“Joy and her husband Les were both medically trained, so they understood the importance of her observation,” says Barran. “But the real message is that anyone can make meaningful health observations—if something feels off, pay attention.”
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