We release a whole fountain of chemicals with different odours through the pores of our skin and when we breathe. Some of these can signal that we are sick, and they can be used to diagnose diseases – sometimes even years before symptoms appear.
It’s nonsense, of course – which is exactly how chemist Perdita Barran reacted when a colleague told her about a Scottish woman who claimed she could smell Parkinson’s disease.
“She probably just smells elderly people, recognises Parkinson’s symptoms and makes some associations,” Barran recalled at the time.
That woman, a 74-year-old retired nurse named Joy Milne, approached Thilo Kunata, a neurologist at the University of Edinburgh, during an event he was speaking at in 2012.
Milne told Kunata that for the first time moreover, she identified another person who had been diagnosed with Parkinson’s disease less than a year later.
“It was really amazing,” Barran says. “She predicted the disease, just like she did with her husband.”
In 2015, news of her amazing abilities made headlines around the world.
Milne’s story is not as incredible as one might think. People’s bodies emit a variety of odours. A new odour can indicate that something has changed or gone wrong in the body.
Scientists are now working on techniques to systematically detect odour biomarkers that could speed up the diagnosis of a range of diseases, from Parkinson’s disease and brain injuries to cancer. The key to detecting them may be hiding literally under our noses.
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It’s just scary to me: people detecting those biochemical signals that appear in the early stages of disease.
As it turns out, Joy Milne was one of the few. She has hereditary hyperosmia, which means her sense of smell is much more sensitive than the average person’s – a kind of ‘super-sniff’.
There are diseases that give off a distinctive odour that is so strong that most people can smell it. For example, the breath or skin of people with diabetes during a hypoglycaemic episode may have a fruity or ‘rotten apple smell’ due to a build-up of fruity-smelling acidic compounds called ketones in the blood. These are formed when the body metabolises fat instead of glucose.
People with liver disease can give off a musty or sulphurous odour when breathing or urinating, and if your breath smells like ammonia or has a “fishy” or you are disease in urine samples with 99% accuracy. Dogs have also been trained to detect early signs of Parkinson’s disease, diabetes, impending epileptic seizures and malaria by smell alone.
But not all dogs are capable of becoming disease detectors, and it takes time to train the capable ones. Some scientists believe that the incredible olfactory abilities of dogs, as well as people like Milne, can be replicated in the lab, perhaps by creating a simple swab that can be sent out for testing.
Barran, for example, uses gas chromatography and mass spectrometry to analyse sebum (oil produced on the skin) from Parkinson’s patients. Gas chromatography separates the compounds and mass spectrometry weighs them to determine the exact nature of the molecules present. The food and perfume industries are already combative – hippuric acid, eicosan and octodecanals. This makes sense because previous research shows that abnormal lipid metabolism is a hallmark of Parkinson’s disease.
“We found that the ability of cells to transport long-chain fatty acids into mitochondria is impaired in people with Parkinson’s disease,” Barran says. “We know that more of these lipids are circulating in these people’s bodies, and some of them are secreted through the skin, and that’s what we’re measuring.”
The team is currently developing a simple skin swab test that could detect Parkinson’s disease in its early stages. GPs usually refer people with symptoms of tremor to a neurologist who makes the diagnosis. This can take years.
We aim to have a very quick, non-invasive test that will effectively triage people so that they )This change in metabolism manifests itself in the distribution of metabolites in different parts of your body,” he adds.
In other words, having a disease can alter the VOCs produced, changing body odour.
Photo by Serenity Strull/BBC/Getty Images
‘We’ve looked at a number of viral and bacterial infections, as well as pancreatic cancer and rabies,’ says Kimball. – ‘I would say that compared to normal health, it’s very rare that we can’t tell the difference between a healthy condition and what we’re studying. That’s a fairly typical result .
But it’s important to note that many of the changes in volatile organic compounds (VOCs) associated with these diseases are too subtle for humans to perceive, so dogs or medical devices can help diagnose some serious but otherwise difficult-to-diagnose diseases in to support recovery,” says Kimball.
And there’s a reason for that. Studies have shown that ketones can serve as an alternative energy source after brain injury and have neuroprotective properties.
Body odour can also signal malaria. In 2018, scientists found that children infected with malaria emit a distinctive odour through their skin, making them particularly attractive to mosquitoes. By studying samples taken from 56 children in western Kenya, the team found a “fruity and grassy” odour that mosquitoes liked very much.
Further analysis of these samples revealed the presence of aldehydes, specifically heptanal, octanal and nonanal, which are responsible for the unique odour. This research could form the basis for a new malaria test. Scientists now hope to recreate this odour and use it as or create biocybernetic organisms,” he adds.
Photo by Serenity Strull/BBC/Getty Images
The RealNose.ai device is currently being developed using real human olfactory receptors – grown from stem cells in the lab – and is finely tuned to detect the myriad odour molecules associated with prostate cancer. The artificial intelligence then looks for patterns in receptor activation.
It’s not enough to know just the components of what’s in the sample,” Mershin says. – The ingredients of a cake tell you very little about the taste or smell of that cake. Everything happens only after your sensors interact with the volatile compounds, and your brain processes that information and turns it into a perception.
“We’re looking for patterns of sensory activation that are closer to how the brain does it,” Mershin adds.
Tim other disorders.
“We don’t use it as much for odour detection anymore,” says Barran. “She can only process a maximum of 10 samples a day, and it’s very emotionally draining. She’s 75 years old, so she’s valuable to us.”
However, if Barran’s method can replicate Joy’s ability to detect Parkinson’s disease in its early stages, it will be a wonderful legacy for Joy and her husband Les.
Joy and Les were people with medical backgrounds, so they knew this observation was important,” Barran says. – But I think the point of this story is that everyone should be confident in their own health and the health of their friend or family, to observe and act if they feel something is wrong .