Human skin emits light (albeit the glow is extremely weak) and a wide variety of small molecules that may be sometimes "sniffed" by dogs or even other humans. These chemicals tell a story about our health and wellness, things we eat and drink, touch and breathe. Mosquitoes use such emissions to assess our "attractiveness" from indicators such as Indoles (unpleasantly smelling but healthy "inner soil" biomarker) or carbon dioxide (amount of which correlates with the size of the person producing it) in the air.
Sampling air for health indicators is much less invasive than drawing blood and could be an invaluable diagnostic tool. Many applications of gas sensors have been proposed over decades ranging from sweat patches to sensorized garments. Where are we now? What is the 2016 state of the art?
We are all different. We respond in our own unique ways to what we eat, breathe, feel and do. And all these environmental influences accumulate over a long period of time impacting our health.
While genomic data and proteomic analyses do not tell the whole story of what might be happening inside our body, metabolic profiling can give a snapshot of how the body works, providing a glimpse into the chemistry between us and our microbiomes.
Can we recognize if people around us are stressed, anxious or fearful without observing their facial expressions, body language and actions or hearing their voice and messages? What about our own stress - assuming we don't rely on heart rate, blood pressure, dry throat, sweating, drops or surges in energy? Yes, we can - by using our nose - as humans, too, recognize and transmit their emotions through chemical senses ...
Despite active foodstagramming and foodteresting, and eagerness to show pictures of meals and diet reports to friends on social media, we don't really want others to know everything we eat. But they might know anyway.
Why worry about NSA, when Google, Facebook, Amazon and many others know what we might be eating. Cameras record our ways to groceries and restaurants, credit cards record our purchases, food chains know our weaknesses, clothes shops know how, as a result, our pant sizes change over time. One day phones will know what we ate too. As both short- and long-term diets change our breath-prints - creating signature metabolites in exhaled breath.
A recent Dutch study actually looked at what gluten-free eating does to our breath. Just 4 week of dieting lead to remarkable - though reversible - differences. (As detected in 20 healthy individuals by gas chromatography coupled with mass spectrometry (TD-GC-tof-MS) in combination with chemometric analysis ). A set of twelve volatile compounds that distinguish gluten-free eaters along with information from Aurametrix knowledgebase is listed in the table below.
Many illnesses are associated with distinct odors. Especially those caused by infectious or opportunistic microbes inside the body or on its surfaces. Body odor of someone infected with C. difficile, for example, can appear "swampy", Rotavirus gives sharply sweet putrid smell that some people associate with wet dogs, H. pylori can create a range of foul odors, and pseudomonas infections can smell like grapes and bitter almonds.