If you’ve ever watched a dog walk around a park, you’ll know the world is jam-packed with scents and smells that are undetectable to the human nose. Compared to most animals, our ability to pick up scents is poor.

But just because we can’t detect many of the smells around us, doesn’t mean they aren’t important. In fact, scientists now believe our own unique smell could reveal vital clues about our health – starting with the smell of our breath and skin.

“Our breath and skin emit volatile organic compounds (VOCs) – gases which come from items such as good, fragranced products and the human body,” explains Aoife Morrin, an associate professor of analytical chemistry at Dublin City University, whose current research is focusing on skin VOCs and what a ‘healthy’ scent looks like.  

“These gases can give us clues about how healthy our different organs are. For example, the VOCs that come from our breath can give us clues about how healthy our lungs are.”

While the idea of using smell to detect the state of someone’s health has been around for quite some time – doctors in ancient Greece used the smell of someone’s breath to diagnose conditions like liver disease and diabetes – scientists are now working to develop diagnostic tools that doctors could use to better detect illness without the need for invasive testing.

Here’s everything you need to know about the link between smell and health – and why relying on VOCs to diagnose health issues could be such an effective tool. 

Before we dive in too deep, let’s just take a closer look at what VOCs actually are. On a very basic level, VOCs are simply gases which are given off by solid or liquid materials. While some VOCs are detectable by the human nose – such as the scent of air fresheners or cosmetics – others, like those given off by building materials or the human body, are undetectable.

In humans, many of the VOCs we release are waste products created by the bacteria and microbes that live within the body’s various microbiomes. Metabolic waste – the waste created by the body as part of the energy production process – is also a source of VOCs.  

“The VOCs which come from our skin mostly come from the microbiome, and the VOC profile [ie the different chemicals being released] can reflect a healthy or altered microbiome,” Morrin explains.

The same is true for our breath, which contains VOCs released by the oral and lung microbiomes. Since these VOCs were first discovered back in 1971, scientists have uncovered hundreds of different types of chemicals which can be found in the breath and reveal signs of infection and disease deeper in the body.

VOCs can also be emitted through our urine, poo, blood and sweat.  

The use of VOCs to identify health issues is a rapidly developing area of research, but some progress has already been made.

For example, Morrin says, VOCs can help dermatologists to measure how acidic someone’s skin is, which in turn can help them predict the health of the skin microbiome. While our skin tends to be on the acidic side – something known as the ‘acid mantle’ helps our skin to kill of harmful bacteria and encourage the growth of healthy bacteria – skin that is too acidic can encourage the growth of bad bacteria and cause imbalances and irritation.

VOCs could also be used in the future to identify bacterial infections, Morrin explains. “We know that VOC profiles change dramatically when a bacterial infection occurs. Wound infections occur commonly in diseases including diabetes and infection monitoring is tricky, so I think VOC monitoring could help in determining infection.” 

Clinics are also already using the urea breath test to detect the bacteria responsible for stomach ulcers, Morrin adds. “I think as this research area grows, particularly in breath, we will start to see more diagnostic tools developed,” she says.

“We could also see consumer products for monitoring our health and well-being through the skin becoming available in the next five to 10 years – maybe simple wearable colour sensors for monitoring the VOCs from our microbiome, for example, to tell us how well our skin bacteria are working to protect us.” 

Images: Getty