Plus how to avoid carrying the parasitic critters home with you.

It's every frequent traveler's worst nightmare: taking home bed bugs. But now, scientists say they've found a way for hotel guests to lower their risk of picking up the invasive, parasitic critters. According to a new study, bed bugs are attracted to dirty laundry—so keeping worn clothes off the floor may help prevent their spread from place to place.

Bed bugs can wreak havoc in hotels and homes, and they’ve recently undergone a global resurgence, the study authors wrote in the journal Scientific Reports. (They’re also getting harder to kill, thanks to a growing resistance to insecticides.)

One possible way the tiny insects spread so far and wide is that they find their way into luggage, or clothing that's packed into luggage. "Hitchhiking seemed the obvious explanation, but a mechanism for this had never been tested," says lead author William Hentley, PhD, a post-doctoral researcher at the University of Sheffield.

Hentley and his colleagues knew that bed bugs are attracted to human odors, and that they can sense more than 100 different chemicals typically present on human skin. To test whether that attraction could extend to recently worn clothing—and not just human bodies—they placed four tote bags in a bedroom-sized lab setting, along with an open container of bed bugs (ick).

Two of the totes contained worn t-shirts and socks, and two contained freshly laundered versions of the same. Sure enough, over the next few days, bed bugs were twice as likely to gravitate toward the bags with the dirty clothes than they were to the clean ones.

The same experiment was also performed in a second room, identical to the first except that it received an increase in carbon dioxide gas—meant to stimulate human breathing. The researchers wanted to see if the presence of carbon dioxide would trigger “host-seeking behavior” in the bed bugs, as it’s been shown to do in other insects.

Their suspicions were right: Bed bugs in the room with carbon dioxide were more likely to leave their “refuge” and search out new spots to settle than those in the room without, with less than 2% remaining in their initial container. And once again, they were twice as likely to head toward the dirty clothes rather than the clean ones.

The study suggests that, when humans are around, bed bugs will actively seek out new hosts. But more importantly, it indicates that if a hotel or other building is infested, leaving yesterday's outfit in an open suitcase or a pile on the floor is seriously asking for trouble.

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"Our study suggests that keeping dirty laundry in a sealed bag, particularly when staying in a hotel, could reduce the chances of people taking bed bugs home with them,” says Hentley.

He adds that, since he's started working with bed bugs, he's much more careful when he travels. "Bed bugs struggle to walk up smooth surfaces, so when I go traveling I always look for those smooth metal luggage racks to keep my suitcase on," he says. "Failing that, I keep my clothes in a big zip lock bag, well away from the bed."