May 22, 2023 -- Anybody who has been on a picnic knows mosquitoes gravitate to some people more than others. An outdoor “smell test” conducted in Africa may partly explain why.
Researchers found that mosquitoes were attracted to human scent that contained a high level of carboxylic acids, which are secretions that protect the skin, said the study published in Current Biology.
Some of those carboxylic acids are also found in “stinky” cheeses such as Limburger, which has long been known to attract mosquitoes. People produce these acids naturally in varying levels but cannot smell them on their skin.
The mosquitoes were much less attracted to the chemical eucalyptol, which is found in plants like sage and eucalyptus trees.
The researchers don’t have any immediate advice for picknickers, but their findings may help develop better ways to combat malaria, Conor McMeniman, PhD, an assistant professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health and Johns Hopkins Malaria Research Institute, told CNN.
Malaria accounts for more than 600,000 deaths per year, mostly in children under 5 and pregnant women. “It inflicts a lot of suffering around the world, and part of the motivation for this study was to try and really understand how mosquitoes that transmit malaria are finding humans,” he told CNN.
Previous studies have been conducted mostly in the lab, whereas this study was conducted outdoors in Zambia in a tent 66 feet square. About 200 mosquitoes in the tent were observed between 10 p.m. and 2 a.m., their most active time.
Six small sleeping tents for human volunteers were set up around the big tent, with each human’s breath and body odor pumped by a long tube into the big tent. The tubes fed into absorbent pads that were heated to a temperature close to a human’s average body temperature.
Infrared cameras observed the mosquitoes’ behavior. “We found that mosquitoes showed an innate preference for certain humans despite navigating in a complex sensory environment with multiple sources of host odor,” the study said.
Afterward, researchers analyzed the volunteers’ skin to come up with a chemical profile of each person. Mosquitoes preferred human scent that contained high levels of carboxylic acids, the study said.