You emit gas. The most obvious and offensive comes from your posterior, but that's not the only gas you emit. Your body is constantly oozing volatile organic compounds (VOCs) -- small molecules that easily enter a gaseous state due to their high vapor pressure -- in breath, sweat, urine, feces, and even saliva. VOCs are responsible, for instance, for the similar aromas that emanate from dairy farms and men's restrooms.

Though the field is still in its infancy, the detection of VOCs may be useful in diagnosing illness or other aberrancies. Perhaps the most infamous VOC test is the Breathalyzer, which detects the presence of ethanol via a redox reaction that converts an orange chemical into a green one.

But, as a review article in the Journal of Breath Research indicates, your breath gives away far more than just your fondness for booze. The presence of acetone, a sweet-smelling molecule that is the active ingredient in nail polish remover, indicates diabetes or starvation. Acetonitrile indicates the person is a smoker; mercaptans (which have a rotten, sulfurous smell) indicate liver disease; dimethylamine and trimethylamine (which smell like urine) indicate kidney failure; and the lack of isoprene indicates lung cancer. Your breath could even be used to detect exposure to pollutants or to help find you in the event you are trapped in a collapsed building.

Your other secretions tell different stories.

Saliva, the authors write, contains "VOCs derived from serum, blood, gingival exudate, nasal cavity, gastrointestinal reflux, food debris, microorganisms, commercial products and environmental pollution," and hence could be used to detect a variety of conditions. Similarly, earwax may reveal information about people's diets and environment. VOCs in urine could help diagnose metabolic disorders, such as Reye syndrome, or a whole panoply of different cancers. Fecal VOCs could indicate infections with pathogenic bacteria, such as Clostridium difficile or Salmonella, as well as inflammatory bowel disease.

The fact that such valuable information about a person's health can be determined simply by analyzing stinky gas molecules has implications about the future of preventive and diagnostic medicine. Still, researchers have a long way to go before a full analysis of your body's VOCs, dubbed the volatilome, becomes reality. Scientists must first compile an enormous catalog of volatilomes that characterize not only diseased and disease-free states, but the natural variation that will occur between healthy humans. That is an enormous task.

However, hopefully soon, it may be common practice at the doctor's office to breathe and/or fart into a device that will diagnose our ailments. A small, smelly, but quiet revolution in medical diagnostics may be brewing.

Source: Anton Amann, Ben de Lacy Costello, Wolfram Miekisch, Jochen Schubert, Bogusław Buszewski, Joachim Pleil, Norman Ratcliffe and Terence Risby. "The human volatilome: volatile organic compounds (VOCs) in exhaled breath, skin emanations, urine, feces and saliva." J. Breath Res. 8 (2014) 034001. doi:10.1088/1752-7155/8/3/034001

(Image: Bad breath via Shutterstock)