Body odour may tell us more than we realise. Beyond the everyday “smells” we associate with sweat or diet, subtle changes in the chemicals our bodies emit through our skin, breath, and sweat can signal underlying health conditions – sometimes years before a diagnosis.

This concept was famously illustrated by Joy Milne, a 74-year-old retired nurse from Scotland, who discovered she could detect Parkinson’s disease through smell. Milne first noticed a musky odour in her husband years before he was diagnosed with the neurodegenerative condition. Later, at a support group for Parkinson’s patients, she realised that many members shared the same unique scent.

Curious to test her ability, researchers at the University of Edinburgh, including analytical chemist Perdita Barran, asked Milne to identify worn T-shirts from Parkinson’s patients. She successfully identified all affected individuals and even detected someone who was diagnosed with Parkinson’s less than a year later. Milne’s story highlighted the extraordinary diagnostic potential of human olfaction – particularly for individuals with hyperosmia, a heightened sense of smell.

While only a few humans possess such super-sensitive noses, researchers are exploring ways to systematically detect these olfactory biomarkers to diagnose a range of conditions. For example:

  • Diabetes: Hypoglycaemia can cause a fruity or “rotten apple” smell due to the buildup of ketones in the blood.
  • Liver and kidney disease: Musty or sulphurous odours from breath or urine, or ammonia-like aromas, can indicate organ dysfunction.
  • Infectious diseases: Certain bacterial or viral infections alter odour patterns, such as sweet-smelling stool in cholera or Clostridioides difficile infections.

Dogs have long been used as medical scent detectors due to their extraordinary olfactory sensitivity, reportedly up to 100,000 times stronger than humans. They have been trained to detect cancers, Parkinson’s disease, diabetes, epileptic seizures, and even malaria, all through scent. However, not all dogs are suitable for training, and it takes considerable time and effort to develop their skills.

To overcome these limitations, scientists are developing advanced diagnostic technologies. Gas chromatography-mass spectrometry, for example, can analyse compounds present in skin sebum to detect Parkinson’s disease. Researchers have identified roughly 30 compounds that consistently differ in patients with the condition, including lipid-related molecules linked to abnormal metabolism. This has paved the way for a non-invasive skin swab test, potentially allowing earlier and faster diagnosis than the traditional referral to a neurologist.

The underlying science revolves around volatile organic compounds (VOCs) – molecules produced during normal cellular metabolism. Diseases can alter these metabolic processes, changing the VOC profile and, consequently, body odour. Innovations in this field are not limited to Parkinson’s: studies are underway to develop VOC-based tests for brain injuries, malaria, and prostate cancer using machine learning and bioengineered olfactory sensors.

Joy Milne now collaborates with Barran and her team to refine diagnostic tests for Parkinson’s and other conditions. While humans like Milne are rare, the research she inspired may soon allow technology to replicate her remarkable olfactory abilities; creating faster, non-invasive, and more accurate methods for early disease detection.

Ultimately, Milne’s story emphasises a broader message: paying attention to changes in your own health, or that of your friends and family, can be meaningful. Even subtle observations could lead to earlier interventions and better outcomes. The future of diagnostics might just be in our noses, or in the sensors that mimic them.

 

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