During the mid-20th century, effective use of pesticides nearly wiped bed bugs (Cimex lectularius) from the developed world. These annoying arthropods seem to have made a comeback in the last two decades, partly enabled by cheap air travel, and partly because the parasite is very good at hopping along for the ride. Though bed bugs can’t jump or swim like flees do, one new study found the critters are at least extremely well equipped to sense human odor, which they follow … along with our dirty underwear, and eventually back into homes or hotels.

Credit: British Pest Control Association, Flickr.

The bed bug isn’t much of a traveler. Instead of being on the prowl for new blood like other parasites like ticks or lice, bed bugs simply lurch in beds and other comfortable establishments which humans also incidentally enjoy. When they do come in contact with humans, they don’t stay long on our bodies. William Hentley, an entomologist at the University of Sheffield in the United Kingdom, was intrigued by this paradox: how can bed bugs be so static and ubiquitous at the same time?

Your laundry: a magnet for bed bugs

He and colleagues had a hunch the parasites were hitching rides on our luggage and laundry. To put this idea to the test, they set loose a whole swarm of bed bugs into a cell placed in the middle of a room where two cotton bags were positioned at equal distances. One was filled with clean clothes while the other was stacked with dirty socks, t-shirts, and other soiled clothing. The volunteers were very happy to oblige but I have a hunch no one wanted them back.

When the experiment was over, the researchers collected the bags and counted the number of bugs found on the surface of the clothing. They found twice as many bed bugs in the bag filled with laundry, the authors wrote in Scientific Reports. 

“There are a lot of good studies out there focused on trying to understand how bed bugs are attracted to humans and how they get around apartment blocks, but no one has really talked about how they get into the house in the first place,” Hentley told Gizmodo. “Stopping people from bringing bed bugs home can be a big step in preventing them spreading throughout the world.”

Previously, researchers found bed bugs have a good nose, being capable of sensing 100 compounds present in the human skin; odors which we spread onto our clothes.

Bed bugs don’t carry disease which makes them pretty benign. In some cases, though, their bitting can cause very annoying rashes or trigger allergies. Credit: Flickr, Louento.px.

Another interesting finding was related to the bugs’ carbon dioxide sensing. Some have suggested the insects sense the gas, which many living things like humans exhale, to find food. When the gas was introduced into the room, the bugs became more alert and interested in finding a meal but the presence of CO2 had little influence when it came to which of the two bags they should choose. This tells us that CO2 is indeed important and prompts the bugs to enter foraging mode, however, the gas doesn’t tell them where to find tasty blood.

On a practical level, the findings confirm that bed bugs are attracted to laundry which means you should be careful how you store them while traveling, especially when staying at a hotel or hostel. Since bed bugs can’t climb smooth surfaces, it’s better if you keep laundry on metal luggage racks. Alternatively, you could keep the dirty clothes in an airtight bag to mask the odor; your roommate might also appreciate this. Most importantly, however, never keep your luggage on the hotel bed else you risk tagging some alone with you back home.