'Invisible' but still real

Invisibility was once a popular theme in science fiction and fairy tales, with invisibility cloaks, invisible enemies, even invisible worlds featured in stories. But invisibility is not necessarily confined to fiction and in the 'real' world there are also a considerable number of 'invisible' things around us.

Invisibility was once a popular theme in science fiction and fairy tales, with invisibility cloaks, invisible enemies, even invisible worlds featured in stories. But invisibility is not necessarily confined to fiction and in the 'real' world there are also a considerable number of 'invisible' things around us.

The old saying 'just because you can't see it, doesn't mean it's not there' is very true. When we switch on the radio in the morning, radio bands and waves can fill our homes with music or the news, even though we cannot see them. Wi-Fi connects to the invisible world of cyberspace, while the magnet field of the earth is all around us. Camoflague can achieve a form of invisibility too, hiding a predator, while the 'hunted' may use it to avoid capture. But perhaps the most prolific invisible substance is the air and the gases it is composed of.

Most school children will learn that the air, in its unpolluted state, is composed of mainly nitrogen, with around a fifth oxygen, one per cent argon and a small amount of carbon dioxide. Unfortunately, pollution of the atmosphere means other more sinister gases may lurk, such as the invisibile and toxic carbon monoxide. 

But not only is the air we breathe in invisible, the air we breathe out is also both invisible and no less complex. The science of respiration and the air we breathe has fascinated scientists over the centuries. Stephen Hales, an 18th century minister and scientist "clarified the nature of the respiratory gases distinguishing between their free (gaseous) and fixed (chemically combined) forms".  Thirteen years after his death in 1761, Joseph Priestly, whose many attributes included being a theologian, philosopher and chemist, isolated an 'air' in 1774 which he detailed in a letter entitled "An Account of Further Discoveries in Air", read to the Royal Society the following year. That 'air' was oxygen. Meanwhile, scientist Joseph Black was busy discovering carbon dioxide and recognised it as a gas that was, amongst other things, "present in gas exhaled from the lung".   

The gas we exhale from our lungs also contains moisture, resulting in a pleasing mist if breathing onto a mirror or venturing out into a frosty morning. However, this gas can reveal far more than just its moisture content. The "potential of exhaled biomarkers, such as volatile organic compounds (VOCs) to improve accurate diagnoses and management decisions in pulmonary diseases" has been under review, and it was noted that "pulmonary diseases seem to be characterized by a disease specific breath-print".  There are many challenges to be mastered however, before their application in clinical practice may come. Moreover, in a study looking at the variation in VOCs in the breath of 50 normal people, gas chromatography and mass spectroscopy was used. This study found that "an average breath sample contained 204.2 VOCs". 

Our breath, it would seem, can potentially contain and reveal considerable detail about ourselves. In the case of halitosis, or 'bad' breath, the significance of the odour of our breath and potential disease was considered as early as the 3rd century BC by the Ancient Greek physician Hippocrates, in his treatise on breath aroma and disease.

While bad breath may be an indicator of an underlying medical condition, it may also originate due to the production of gases from within the oral cavity. These gases, or Volatile Sulphur Compounds (VSCs) are comprised of hydrogen sulphide, methyl mercaptan and dimethyl sulphide and occur as a result of bacteria in the mouth.  As the bacteria degrade, these gases are formed.

In the case of VOCs referred to earlier, breath and its biomarkers may have potential to be used as an aid in the diagnosis of certain conditions. With regard to VSCs emanating from the oral cavity, these may also point to the existence of possible conditions. However, in the case of VSCs, an individual may be aware of and recognise the odour they are responsible for, even though as gases, they are 'invisible'. 

Halitosis can prove a potential source of embarrassment to sufferers and for some, it may result in social or psychological difficulties.  Some sufferers may be unaware of

having the condition until told by another, or by their dentist.  

Treating halitosis originating from the oral cavity is likely to include improving the sufferer's dental hygiene. Products offering temporary relief from the symptoms of bad breath may only however, mask the smell. CB12 works by neutralising the VSCs using a combination of low concentrations of zinc acetate and chlorhexidine, providing relief from the symptoms of bad breath for up to 12 hours.

Even things that are 'invisible' can affect us, but in recognising that they are there, something can be done.


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