Harnessing Our Sense of Smell for Earlier Disease Identification

Scents are portals that can transport us to specific memories and experiences. Perhaps the aroma of baked vanilla reminds you of weekends at your grandmother’s house, or maybe the stench of Axe body spray brings you back to the scene of a disastrous prom. When it comes to using our senses to diagnose medical conditions, our noses may not be the first thing that comes to mind. However, emerging evidence suggests that olfaction - the sense of smell - can be a powerful tool in advancing early disease identification.

The extraordinary nose of Joy Milne

Joy Milne, a nurse from the United Kingdom, has a condition called hereditary hyperosmia. She is genetically predisposed to have a heightened sense of smell, and noticed that she could smell diseases on patients throughout her nursing career. Her keen sense of smell was brought to the attention of researchers when her husband was diagnosed with Parkinson’s disease: she had been aware of a ‘musky, dank odour’ on him for 12 years — and when she stepped foot inside a Parkinson’s UK support group, she realised the people there had the same smell.

With this epiphany, Milne contacted neurobiology researchers, who discovered that she could detect Parkinson’s disease with 95% accuracy just by smelling the person’s clothing and swabs for sebum (oil produced by the skin). Armed with newfound confidence in her ability to predict illness from scent alone, Milne now works across the globe to determine the smells of other diseases, including cancer and tuberculosis.

Sniffer dogs - not just for airport security

A professor once told Milne that her superb sense of smell makes her closer to a dog than a human. Although she took that as a compliment, it raises the question of whether man’s best friend could be Milne’s colleague in advancing early diagnosis through olfaction.

The ability of dogs to detect smells is reported to be 10,000 to 100,000 times stronger than that of the average human, and we have long exploited this ability for various purposes. Sniffer dogs are responsible for a myriad of services: from detecting illegal substances to locating survivors at disaster sites. Medical detection dogs are a specific class of sniffer dogs that are trained to recognise changes in scent caused by rises and dips in certain chemical compounds within the human body. They can alert patients with diabetes of low blood sugar, predict epileptic seizures and even identify cancer; they can also detect infectious diseases, including malaria and COVID-19.

While we are familiar with medical detection dogs’ capacity to support patients in their daily lives, researchers are exploring the potential of using them as a non-invasive screening method. However, we need to standardise training and deployment protocols and ascertain reproducibility with larger sample sizes before our furry friends become a mainstay in disease diagnosis.

Leading early diagnosis by the nose

When Joy Milne or a medical detection dog smells disease, they are actually detecting the presence of Volatile Organic Compounds (VOCs) which are produced by various biological processes. Researchers are attempting to emulate their ability to detect the smell of disease by developing electronic noses, devices that enable the analysis of VOCs. A typical electronic nose uses a gas sensor array connected to a pattern recognition algorithm which identifies the types and concentrations of VOCs in the sample.

VOCs are increasingly recognised as biomarkers that show significant promise in diagnosing various diseases, particularly respiratory diseases such as asthma and chronic obstructive pulmonary disease. The noninvasive nature of screening diseases by olfaction makes it an attractive alternative to traditional blood testing and biopsies. Therefore, advancements in electronic nose systems and medical detection dog deployment hold great promise in our crusade for earlier disease diagnosis.

References

Image taken from Cambridge Filmworks and Medical Detection Dogs

Jendrny, P. et al. (2021) ‘Canine olfactory detection and its relevance to medical detection’, BMC Infectious Diseases, 21(1). doi:10.1186/s12879-021-06523-8.

Jenkins, E.K., DeChant, M.T. and Perry, E.B. (2018) ‘When the nose doesn’t know: Canine olfactory function associated with health, management, and potential links to microbiota’, Frontiers in Veterinary Science, 5. doi:10.3389/fvets.2018.00056.

Kulbatski, I. (2023) Disease scent signatures disclose what the nose knows, The Scientist. Available at: https://www.the-scientist.com/disease-scent-signatures-disclose-what-the-nose-knows-71161 (Accessed: 04 May 2025).

Milne, J. (2022) Experience: I can smell illnesses in people, The Guardian. Available at: https://www.theguardian.com/lifeandstyle/2022/oct/21/experience-i-can-smell-illnesses-in-people (Accessed: 04 May 2025).

Moura, P.C., Raposo, M. and Vassilenko, V. (2023) ‘Breath volatile organic compounds (VOCs) as biomarkers for the diagnosis of pathological conditions: A Review’, Biomedical Journal, 46(4), p. 100623. doi:10.1016/j.bj.2023.100623.

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