A new study examines how varying levels of heat and humidity affect bed bugs (Cimex lectularius). Generally, low humidity decreases bed bug survival, but the most lethal combination found in the study was high humidity (90%) and high heat (40 degrees Celsius). Shown here are bed bugs that were dead after 24 hours at the high-heat, high-humidity treatment in the study. (Photo by Bandana Shrestha)

By Andrew Porterfield

Andrew Porterfield

Bed bugs (Cimex lectularius) are common in northern temperate zones and feed on human blood. They usually are found in mattresses and bedding material, taking blood meals at night. While the bed bug’s survival depends heavily on temperature and relative humidity, little is known about how much heat and humidity can prove lethal.

Decades ago, bed bugs were more prevalent and believed to be associated with dilapidated housing. In recent years, however, the insect has made a resurgence, often appearing in well-maintained houses and even luxury hotels. Entomologists believe that factors including increasing global travel, easily moved bedding items, insecticide resistance, and types of pesticides used may lie behind this resurgence. These factors also point to a need to develop more effective ways of managing bed bug infestations.

To test heat and humidity effects on bed bugs, Aaron Ashbrook, Ph.D. (right), assistant professor of entomology at Louisiana State University, and graduate student Bandana Shrestha (left, now at the University of Kentucky), tested male bed bugs for tolerance to increasingly high temperatures and three relative humidity levels. Their study was published in November 2025 in the Journal of Economic Entomology. (Photo by Sadiq Shaik)

To test heat and humidity effects on bed bugs, Aaron Ashbrook, Ph.D., assistant professor of entomology at Louisiana State University, and graduate student Bandana Shrestha (who now is at the University of Kentucky), tested male bed bugs for tolerance to increasingly high temperatures and three relative humidity levels. The researchers found that, as temperatures rise, so does bed bug mortality. Drier (lower humidity) environments also triggered stress and bed bug death. Their study was published in November in the Journal of Economic Entomology.

Ashbrook and Shrestha placed the bed bugs into plastic petri dishes, modified to allow exposure to environmental conditions. The experiment tested five temperatures (25, 27, 38, 39 and 40 degrees Celsius), and three relative humidity conditions (10%, 45%, and 90%). Bed bugs at 25 degrees and 45% humidity were the control group. Mortality rates were measured after 14 days.

The results showed that, at 37 degrees C, bed bugs had higher median survival times at 45% and 90% humidity, indicating that the insects’ physiology may be helping them survive heat stress. Survival declined to 12 days at 37 degrees C with 10% humidity, and survival times decreased to 4-6 days at 39 degrees C at 10%, and just three days at the same humidity and 40 degrees C. Mortality was highest at 40 degrees C at all humidity levels, with one day survival at 90% humidity.

These results were surprising. “We did not anticipate that bed bugs would survive so long at some of the tested temperatures,” Ashbrook says. “At 37 degrees C and standard indoor humidity (45%), approximately half the bed bugs were still alive after two weeks.”

A new study examines how varying levels of heat and humidity affect bed bugs (Cimex lectularius). Generally, low humidity decreases bed bug survival, but the most lethal combination found in the study was high humidity (90%) and high heat (40 degrees Celsius). To conduct the study, researchers placed the bed bugs into plastic petri dishes, modified to allow exposure to environmental conditions, shown here. The experiment tested five temperatures (25, 27, 38, 39 and 40 degrees Celsius), and three relative humidity conditions (10%, 45%, and 90%). (Photo by Bandana Shrestha)

“One of the biggest surprises for me,” Shrestha says, “was how strongly the effects depended on specific temperature-humidity combinations rather than tested temperature alone. At 37 degrees C, humidity had very little influence on survival, which was unexpected given bed bugs’ need to maintain water balance.”

Exposure to dry environments, the study shows, seems to be more effective at causing mortality. However, Ashbrook and Shrestha also found what appears to be a critical threshold at 39 degrees C, at which high humidity (90%) caused complete mortality at 5 days.

The researchers still recommended high heat with low humidity as the most practical and effective condition for controlling bed bugs. “While low humidity was less effective than high humidity, high heat with low humidity was the second most effective condition,” Ashbrook says.

Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He is based in Camarillo, California. Connect with him via LinkedIn or via email at [email protected].