Sense of smell

Sniffing out the true value of smell

Image credit: Dreamstime

Even after evolutionary changes, humans are still able to differentiate one trillion smells. This dwarfs the 10 million colours that can be distinguished.

One of the symptoms of the bubonic plague is a nasty-smelling rash on the skin. In the 17th century, people carried an assortment of fragrant herbs to mask the smell. (The rash is the ‘ring o’ roses’ and the herbs are the ‘pocketful of posies’ in the nursery rhyme.)
As medicine has advanced, understanding smell rather than masking it has become an area of research. Gas sensors can test the components in someone’s breath to indicate some diseases.

In 2018, Fujitsu Laboratories developed a portable breath sensor as an alternative to large analytic instruments used to detect high blood pressure, diabetes and cancer. The breath sensor analyses gas components which enter the breath from the body’s organs, and which evaporate in the lungs to be exhaled in the breath. Specific gas components can be an indication of some health conditions. For example, ammonia concentration is correlated with liver metabolism and the infection Helicobacter pylori. Combined, these are risk factors for stomach cancer.  

Rather than analysing the difference in response patterns between breaths, which an ‘electronic nose’ would do, the breath sensor uses copper bromide film to adsorb ammonia molecules, which increases resistance on the device’s electrode.

The copper bromide is a P-type semiconductor which adsorbs ammonia molecules. Once the gas is isolated, it is measured at a concentration level of 10 parts per billion. An algorithm based on the increased resistance on the electrode delivers the ammonia concentration result from as little as 10 seconds of exhalation.

The next steps are to increase the types of gases that can be detected, starting with acetone, and in time, incorporate the breath sensor into smartphones and wearable devices.

In another area of research, the Michael J Fox Foundation for Parkinson’s Research is funding work to study a unique scent on the skin of people with the condition.

In 2015, a nurse who has a heightened sense of smell reported a musty, musky, yeasty smell on her husband before he was diagnosed with the disease. Classified as a ‘super smeller’, she noticed the same scent in his Parkinson’s support group members and is now working with researchers to identify this particular scent, which is thought to come from the skin’s sebum and is unaffected by medications and supplements. If it can be isolated as a biomarker it could potentially be used to diagnose and monitor Parkinson’s.  

Sense of smell

Image credit: Dreamstime

Instead of using the olfactory receptors to detect volatile compounds in the air and send signals to the brain, an electronic nose, or e-nose, is a chamber with sensors which measure physical changes in chemical compounds. The signals are sent to a computer, which extracts key characteristics to create a pattern classification algorithm of the aroma. E-noses are used to ‘sniff out’ volatile organic compounds in pharmaceuticals, explosives, food and drink.

Adding AI can broaden its scope. At Sweden’s University of Gävle, researchers have developed an e-nose which uses AI, measuring changes in the acetic acid content and blowing air to add oxygen, which releases substances from the wine for a more accurate reading. José Chilo, researcher in electrical engineering at the university, likened it to a sommelier aerating wine before tasting. The e-nose prototype is intended for winemaking but could be used to assess the quality of an aged wine, without risking a connoisseur falling ill or impacting their sense of smell.

AR/VR is taking aromatherapy treatments to  a new level. Relax VR, for example, has developed a VR headset specifically for spa use. It is more hygienic, with less foam cushioning than gaming headsets, offers a wider 101° field of vision and is Bluetooth-connected to noise-cancelling headphones for immersive audio. Felt pads with essential oils are applied to the headset for olfactory stimuli. Combined with spa treatments, the fully immersive experience is said to deepen the relaxation experience.

OVR Technology uses scent cartridges rather than essential oils, integrated into its VR headsets. The ION Scentware cartridges are created from molecules of eight primary aromas that can be blended or used ‘solo’ to enhance the VR experience. OVR Technology suggests a rose garden where the wearer can pick flowers and experience their perfume or revisit camping expeditions, with the smell of a campfire and toasted marshmallows.

The Olfactory Virtual Reality headset can also be used in exposure therapy. A three-week programme at the University of Central Florida used the headsets to gradually expose people suffering from PTSD to triggering scents, sights and sounds in a safe, controlled virtual environment. Founder and CEO, Aaron Wisniewski, reports that 66 per cent of participants were symptom-free at the end of the course, achieved without the use of drugs.

The headsets could also be used to market holidays or travel tours or enhance holiday or event photographs with a smell that transports you back to that nature trail or beach wedding.

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