Take a look at your skin. It’s an integral part of your body and your largest, most visible organ. The tone and complexion of it help define your appearance.

It’s also home to a population of bacteria that reflect your environment, from the abode you live in to the city where you reside. A careful balance of these bacteria helps keep you healthy. Too many or too few, and you might get sick.

There’s still much to learn about these little hitchhikers and how they affect our health. Thanks to researchers from the University of Oregon, we have one more piece of the puzzle. Through a somewhat unconventional study, they learned just how transferrable our skin bacteria can be. By studying women’s roller derby teams, they observed some fascinating patterns.

The researchers swabbed the upper arm skin of the players on three teams before a tournament. Each team was from a different state. Players on the same team all had similar populations of arm-skin bacteria. Teammates’ samples were so alike that scientists could tell which team a woman belonged to just by analyzing her bacterial samples.

After a match, called a bout, there was less uniformity. Bacteria originally found on California players appeared on Oregon players, for example, and vice versa.

So, what’s the point? For one thing, knowing how easily skin-dwelling bacteria transfer between people can help scientists understand the risks of acquiring dangerous bacteria.

There’s also a massive project underway, called the Human Microbiome Project, to learn more about the bacteria that routinely live on and in human bodies. It eventually may reveal much about how our bodies work and the illnesses that plague us.

For now, try not to be too grossed out by the thought of swapping skin bacteria with those around you. You’ve been doing it your entire life.