By David Shultz
On the surface, bed bugs seem ill-equipped for world domination: They can’t fly, jump, or swim; they can survive only on blood; and the world’s foremost apex predators—humans—want them all dead. Yet the parasitic arthropods have recently undergone what scientists are calling a “rapid global expansion,” taking over new territories and growing in number and range. And according to a new study, their globetrotting is made possible in part by an unusual form of transportation: our stinky laundry.
“It’s a good study,” says Richard Cooper, an entomologist at Rutgers University in New Brunswick, New Jersey, who was not involved with the work. He says it makes sense that the bugs are attracted to human odors, even on clothing.
Though they aren’t known to transmit disease, bed bugs (Cimex lectularius) can leave behind itchy bites and cause allergic reactions. In the middle of the 20th century, the pests had been largely eradicated from large parts of the developed world, but bans on effective pesticides in the 1990s, along with cheap air travel, have allowed the bugs to come creeping back.
Unlike ticks or lice, the apple seed–sized bed bugs aren’t travelers: They don’t stay on their hosts for long, and they rarely leave the beds and couches where they feast. So how were they getting onto planes?
“To me, hitchhiking seemed like the best explanation,” says William Hentley, an entomologist at the University of Sheffield in the United Kingdom. “That then led me to this question of whether they’re attracted to our clothes and the smell of humans.”
To figure out whether the bugs were indeed stowing away in our laundry and luggage, Hentley and his colleagues tested whether the insects were attracted to soiled clothing. They set a cage full of bed bugs in the middle of a room and placed two cotton bags at equal distances—one filled with clean clothes and the other filled with dirty socks and T-shirts collected from volunteers. The researchers released the bed bugs from the cage and let them wander freely for 96 hours.
At the end of the experiment, about twice as many bugs were attracted to the dirty clothes as to clean ones, the team reports today in Scientific Reports. That jives with prior experiments that have shown that bed bugs can smell more than 100 compounds produced by human skin—many of which could easily linger on clothes for multiple days, the researchers say.
They also tested whether increases in carbon dioxide—long thought to signal a nearby meal—made the bugs more or less likely to go for the smelly clothes. When added to room, the gas seemed to trigger foraging behavior, but the bugs weren’t any more likely to go for the dirty clothes than they were initially. That suggests that carbon dioxide prompts the bugs to forage, but it doesn’t help them home in on the smelly laundry, the team concludes.
So what can you do to keep the six-legged parasites out of your suitcase when you travel? Hentley is careful to point out that he hasn’t studied these techniques scientifically, but he recommends simply putting your bags up on the metal luggage racks in a hotel room, because the bugs can’t climb up smooth surfaces. If no such rack is to be found, keeping your soiled garments in an airtight bag should help mask the smell. But bear in mind that if you’ve previously put dirty clothes in your luggage, you might need to wrap up your whole suitcase, he says.
Cooper agrees that plastic bags might work, but he doesn’t use them himself. “The biggest thing is not keeping your luggage on the bed,” he says. Another option: putting your bags into a portable heating chamber whenever you get home and washing and drying your clothes on high heat. “Heat is the Achilles heel of the bed bug,” Cooper says.