What makes your body different from everyone else's? Maybe you're thinking fingerprints or the DNA that you leave on everything you touch. Now, add your breath to that list. Researchers have found that individuals have unique "breathprints" that change throughout the day and that reflect chemical reactions going on in the body. In the new study, reported today in PLOS ONE, volunteers blew air into a mass spectrometer (pictured), which split the exhalation into its chemical components. Unlike older methods, which required samples to be prepared and then injected into the machine, the device used in this study can directly accept breath and show the results in seconds. The researchers found that individuals' breathprints changed slightly from sample to sample, but always kept a core signature that was unique enough to identify that person. That means that a breathprint reflects what's going on in a person's body and isn't just a random sampling of room air, they conclude. In the future, the authors say that such a technique could reveal the drugs you've been taking or biomarkers of diseases such as cancer. Smaller versions of the machine shown above could make their way into doctors' offices and could be used to detect doping at races without sending samples to a lab.

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