Pores for thought: how sweat reveals our every secret, from what we've eaten to whether we're on drugs

Simona Francese was able to analyse my index fingerprint when I placed it on a slide in a lab. It felt like I was giving her my password to my body's secrets. Francese, a Sheffield Hallam University forensic scientist, analyzes the chemicals in those swirls and whirls. While most forensic scientists look at a fingerprint pattern, Francese is a Sheffield Hallam University forensic scientist. She hopes to create techniques that allow her to identify victims of crime from the sweaty residues left behind.The sweat ink on our fingers is a body fluid that contains information about our health, and vices. Your sweat glands produce perspiration from the blood's watery components. Any chemicals that circulate around your circulatory system may leak out of your sweat pores.Francese quickly found evidence of my morning cup of coffee thanks to the caffeine in my blood when she took my fingerprints. Francese used mass spectrometry to analyze my fingerprints. Francese might have also detected if I had spiked my morning latte with whisky or taken a line of cocaine to get me through the day. Francese has actually tested her method in conjunction with law enforcement. She found chemical evidence that the stalker had been using alcohol and cocaine, something he also admitted to to law enforcement.Our sweat contains more than mind-altering chemicals. South African nurses were able to turn their sweat red due to their intense love for spicy tomato corn chips. Scientists found that her sweat was reddish due to her love for chips and immortalised her affection for Nik Naks in medical literature.Researchers are also looking for ways to differentiate vegans from meat-eaters using sweaty fingerprints and biological sex. Francese states that fingerprints are not inanimate objects for those who have been trained in chemistry. It is possible to discover organic and inorganic material.Also, sweat contains markers for certain types of cancers.It's not only forensic scientists that are interested in the sweat we produce throughout the day. Even though fingerprints are among the least noticeable of sweaty marks in the body, we still leave behind a lot of perspiration on our bikes, yoga mats and T-shirts. We may soon be able use this measurement to find out more about ourselves in the age of personal measurement.Engineers are creating adhesive patches that can be embedded with electronics to collect and analyse sweat. This information could then be transmitted to smartphones. This technology could be integrated into smartwatches that analyse sweat from the skin.The future smartwatches will monitor your alcohol levels and alert you when it is time to hail a taxi. The future car may have a fingerprint pad, which will require drivers to test for intoxicants before it can start. A coach might decide to monitor athletes to improve their training programs. This is based on lactate levels that are calculated from sweat during a workout. A player who releases biomarkers of fatigue or stress in their sweat may be replaced by someone else during an important match.Many sweat-patch developers want to accurately measure glucose. This is a surprising goal because skin bacteria consumes glucose as soon it touches the surface. But the hope is that people with diabetes won't have to rely on needles for accurate glucose monitoring.Like most technological innovations, sweat monitoring has both progressive and dystopian potential. It could be disturbingly easy for health insurance companies to detect pre-existing conditions and for employers to perform drug testing. There is also the possibility of civil liberties being violated by law enforcement fingerprint analysis. Law enforcement in the US can secretly collect DNA from someone's hair or saliva from a coffee cup. The UK samples DNA from people arrested for criminal offenses. Even though it will likely take many years for fingerprint chemical analysis to become mainstream, the process of collecting fingerprints from suspects would be easier than obtaining a DNA sample.You should also consider tech privacy protocols. What happens if smartphones and smartwatches can track our sweaty secrets?Many people complain about their sweat odour and the wet patches that it leaves behind. However, it is fascinating to see the hidden secrets of human biology. We scroll through Francese's list of chemicals Francese found in my index fingerprint. I was overwhelmed by the amount of information my body can give us, especially on hot summer days.On 13 August, Sarah Everts' The Joy of Sweat: A Strange Science of Perspiration (WW Norton) will be published. To support the Guardian, order your copy at guardianbookshop.com. Delivery fees may apply.