Bed bugs, once thought to have disappeared, have returned. Interest in the issue is rising again after accounts were posted online claiming bed bugs were found at a hotel in Gangnam, Seoul.

Bed bugs are bloodsucking insects that feed on the blood of people and animals. They do not transmit infectious diseases, but bites can cause intense itching and skin rashes. Because multiple areas are often bitten in succession, lines of red marks may appear. Persistent scratching of itchy sites can lead to secondary infection or trigger allergic reactions.

Contrary to common belief, bed bugs are not pests that arise because a home is dirty. They have little to do with cleanliness. They track body heat and carbon dioxide, and if there is any crack to hide in, they can settle anywhere, from luxury hotels to ordinary homes. Tell-tale signs include black specks of feces on mattresses and bedding, rusty or brown blood stains, and cast exoskeletons shed like husks.

With the increase in overseas travel, concern about the introduction of bed bugs is also growing. Bed bugs have flat bodies about the size of an apple seed, allowing them to hide in very narrow crevices. The U.S. Centers for Disease Control and Prevention (CDC) lists mattress seams, bed frames, headboards, behind wallpaper, and gaps in furniture as major hiding spots. They are primarily active at night and emerge while people are asleep.

Online travel communities even share a ‘bed bug check routine’. Upon arriving at a lodging, place your suitcase on the bathroom floor or in the tub rather than on the bed, then inspect the mattress corners and the area around the bed before unpacking.

After returning from a trip, it is recommended to immediately launder worn clothing or run it through a dryer, and to inspect luggage before bringing it indoors. Bed bugs are vulnerable to heat, so high temperature treatment using a dryer, a steam iron, or a steam cleaner is used for control. Clothing and bedding can be rid of bed bugs and eggs through high heat drying.

Pest control professionals also advise that rather than indiscriminately spraying insecticides when bed bugs are found, it is more effective to seek professional treatment. Because they can hide deep in furniture crevices and within walls, removing only the visible individuals often does not solve the problem. Experts say, “Bed bugs are pests more adept at movement and hiding than at exploiting a lack of cleanliness,” and add, “Managing luggage after travel and early detection are the most effective preventive measures.”