If you ever saw the comic Peanuts, which gave the world Snoopy and Charlie Brown, you’ll remember that there is one character, Pig Pen, who constantly had a cloud of dirt surrounding him. If you ever ran into Pig Pen on the street, you’d probably cross to the other side to avoid him. However, new research shows you probably have a lot more in common with Pig Pen than you’d like to think.

According to a study published in PeerJ, each of us is surrounded by a cloud of bacteria every second of our lives. These microbial companions are so unique that the cloud might be as identifiable as your fingerprint.

The study was relatively small — just 11 participants — but it brings evidence that our microbial footprints may be as good as an actual footprint at identifying us. Researchers put the subjects inside a sanitized chamber for 90 minutes, then tested the cloud of microbes each subject left behind. Previous research found that we put our microbial footprint into the room we’ve just entered relatively quickly, with your house having different mircobiomes than your office or the hotel room you spent a vacation in.

The subjects left behind plenty of common, human-associated microbes, but the ratios of these microbes were unique enough that researchers were able to identify nearly all of the subjects just based on their microbial footprints.

"We expected that we would be able to detect the human microbiome in the air around a person, but we were surprised to find that we could identify most of the occupants just by sampling their microbial cloud," said lead author James F. Meadow, a postdoctoral researcher formerly from the Biology and the Built Environment Center at the University of Oregon, in a press release.

The most interesting aspect of the study may be the implications it has on forensic evidence used in crimes. As anyone who has watched CSI knows, DNA evidence can lead to a solid guilty or innocent verdict in a crime. But sometimes there is no DNA, so with what we know about microbial footprints, forensic analysts may turn to the microbial clouds for evidence. A study last year suggested microbial footprints may be used in sexual assault cases if there is an absence of DNA. In Hawaii, a different group is trying to figure out if microbes left on or around homicide victims could tie a suspect to the crime.

Source: Meadow, J, et al. Humans differ in their personal microbial cloud. PeerJ . 2015.