Hundreds of chemicals flow from our bodies into the air every second. These chemicals release easily into the air because they have high vapor pressures, causing them to boil and turn into gases at room temperature. They give clues to who we are, and how healthy we are.
Since the time of ancient Greece, we know that we smell different when we are sick. Although we rely on blood analysis today, ancient Greek physicians used smell to diagnose illnesses. If they took a drop of your breath and described it as fetor hepaticus (meaning bad liver), it meant you could be headed for liver failure.
If a person’s whiff was sweet or fruity, physicians thought that this meant that sugars in the digestive system were not being broken down, and that person probably had diabetes. Science has since shown that the ancient Greeks were right – liver failure and diabetes and many other diseases including infectious diseases cause your breath to smell distinctive.
In 1971, Nobel Laureate chemist Linus Pauling counted 250 different gaseous chemicals in the breath. These gaseous chemicals are called volatile organic compounds or VOCs.
Since Pauling’s discovery, other scientists have found hundreds of other VOCs in our breath. We have learned that many of these VOCs have distinct odors, but some have no odor that our nose can detect.
Scientists believe that whether VOCs have a smell that our nose can detect or not, they can reveal information about how healthy a person is.
His wife, nurse Joy Milner, recognized a Scottish man with Parkinson’s disease after she was convinced that the way he smelled had changed, years before he was diagnosed in 2005. This discovery has led to research programs related to Joy Milner to identify the precise. the smell of this disease.
Dogs can sniff out more diseases than humans because of their more sophisticated olfactory talents. But more subtle changes in the profiles of VOCs linked to gut, skin and respiratory diseases as well as neurological diseases such as Parkinson’s come with technological techniques, such as mass spectrometry analytical tools. Researchers believe that some diseases will one day be diagnosed by breathing into a device.
Where do VOCs come from?
Breath is not the only source of VOCs in the body. They are also emitted from skin, urine and faeces.
VOCs from the skin are the result of millions of skin glands removing metabolic waste from the body, as well as waste generated by bacteria and other microbes that live on our skin. Sweat produces additional nutrients for these bacteria to metabolize and can result in foul-smelling VOCs. However, the smell of sweat is only part of the odors from VOCs.
Our skin and gut microbiome are made up of a delicate balance of these microbes. Scientists think they influence our health, but we still don’t understand a lot about how this relationship works.
Unlike the gut, the skin is relatively easy to study – you can collect skin samples from living people without going deep into the body. Scientists think that skin VOCs can provide insights into how the bacteria of the microbiome and the human body work together to maintain our health and protect us from disease.
In my team’s lab, we are investigating whether the skin’s VOC signature can reveal different characteristics of the person it belongs to. These signals in skin VOC signatures are likely how dogs distinguish humans by smell.
We are at a fairly early stage in this area of research but we have shown that you can tell men from women based on how acidic the VOCs are from the skin. We use mass spectrometry to see this because the average human nose is not sophisticated enough to detect these VOCs.
We can also predict a person’s age with reasonable accuracy within a few years from their skin VOC profile. This is not surprising as oxidative stress in our bodies increases as we age.
Oxidative stress occurs when your antioxidant levels are low and causes irreversible damage to our cells and organs. Our recent research found the byproducts of this oxidative damage in skin VOC profiles.
These VOCs are not only responsible for personal smell – plants, insects and animals use them as a means of communication. Plants are in constant VOC dialogue with other organisms including pollinators, herbivores, other plants and their natural enemies such as harmful bacteria and insects. VOCs used for this back-and-forth dialogue are called pheromones.
What has science shown about love pheromones?
In the animal kingdom, there is good evidence that VOCs can act as aphrodisiacs. For example mice have microbes that contribute to a highly odorous compound called trimethylamine, which allows mice to identify a potential mate species. Pigs and elephants also have sex pheromones.
People may also produce VOCs to attract the perfect person. Scientists have yet to fully decode skin – or other VOCs released from our bodies. But evidence on human love pheromones so far is controversial at best. One theory suggests that they were lost around 23 million years ago when primates developed full color vision and began to rely on their enhanced vision to choose a mate.
However, we believe that whether human pheromones exist or not, skin VOCs can reveal who and how we are, in terms of things like aging, nutrition and exercise, fertility and even stress levels. This signature probably contains markers we can use to monitor our health and diagnose disease.
This article from The Conversation is republished under a Creative Commons license. Read the original article.
Aoife Morrin receives funding from Science Foundation Ireland.