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How do bedbugs travel? They like dirty laundry, study finds

Bedbugs do not pose a serious health hazard. Only in very rare cases, when someone is allergic to them, do they lead to illness. But the bites can itch and trigger a mild skin rash.

An oblique-dorsal view of a bed bug nymph ingesting a blood meal from the arm of a human host.
CDC/Piotr Naskrecki

Thanks in part to a rise in international travel, bedbugs have experienced a global resurgence during the past two decades. People often bring bedbugs home with them from a trip — and not just when the itinerary included seedy motels. Five-star hotels have also been plagued with infestations of these tiny, oval-shaped, blood-sucking arthropods.

Fortunately, bedbugs do not pose a serious health hazard. Only in very rare cases, when someone is allergic to them, do they lead to illness. 

But the bites can itch and trigger a mild skin rash. And then there’s the creepiness factor — the knowledge each night as you crawl into bed that insects will be biting and consuming your blood as you sleep.

An entomological mystery

One of the big mysteries regarding bedbugs has been how they have become such good travelers. To begin with, they are wingless. Also, unlike lice or ticks, bedbugs do not stay on their hosts for long. After they have fed, they crawl back into crevices or holes near where their hosts sleep.

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So how, exactly, are they getting people to take them home with them in their suitcases?

Apparently, by stowing away on the traveler’s dirty laundry. According to a simply but cleverly designed new British study, when bedbugs can’t find a human host, they will seek out items — specifically, soiled clothing — that contain human odors.  

“Our results show, for the first time, how leaving worn clothing exposed in sleeping areas when traveling can be exploited by bedbugs to facilitate passive dispersal,” the study’s authors conclude.

The study was published late last week in the journal Scientific Reports.

How the study was done

For the study, researchers at the University of Sheffield conducted two experiments in identical, temperature-controlled (around 71 degrees Fahrenheit) rooms. One of the rooms had, however, a slightly higher level of carbon dioxide to imitate the presence of a human breathing in the room. It’s known that bedbugs are attracted by the carbon dioxide that humans exhale.

Each room had four clean, cotton tote bags. Two contained clothes (white cotton T-shirts and socks) that had been worn by four volunteers during about three hours of normal daily activity. The other two bags contained clean versions of the clothes. 

A container of 10 (five female, five male) just-fed (on human blood) bedbugs was placed in each room for 24 hours before the bags were brought in. After another 24 hours, the top to the container was lifted, allowing the bedbugs to roam free. Four days later, the researchers tracked down each bedbug and recorded where it was found.

The experiment was repeated six times. Between each experiment, bleach was used to clean the rooms.

An analysis of all the data from the experiments revealed that the bedbugs were about twice as likely to be on or near the tote bags with the worn clothing than the ones with the clean laundry.

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The level of carbon dioxide in the room had no effect on this finding. Bedbugs in the high-carbon dioxide room were, however, more likely to leave the container. 

What travelers can do

So, what can you do when traveling to lower your risk of bringing these nasty little bugs home with you?

In an accompanying press release, the authors of the study suggest putting your suitcases and other bags up on the metal luggage racks often found in hotel rooms. (Non-metal luggage racks may contain bedbugs, so inspect those racks carefully before putting your bags there.)

Don’t put your bags (or clothing or any other personal items) on the bed.

They also recommend keeping your dirty laundry in a sealed plastic bag while staying in a hotel.

Then, when you get home, be sure to use high heat to wash and dry all your traveling clothes. Heat kills bedbugs. Freezing temperatures do, too. So if you have clothes that can’t be washed on high heat, you can put them in a freezer for about four days.

FMI: You’ll find the full study on Scientific Reports’ website. Also, the University of Minnesota Department of Entomology has a terrific website about bedbugs, which includes information for travelers on how to inspect a hotel room for signs of them.