Mosquito magnet? There’s a chemical reason for that

If you’ve ever wondered why you get targeted by mosquitoes while your friends and family escape unscathed, according to a new study, the answer might lie in the chemicals on your skin specifically, carboxylic acids (Cell 2022, DOI: 10.1016/j.cell.2022.09.034).

A team of researchers led by Leslie Vosshall of Rockefeller University studies how the Aedes aegypti mosquito sniffs out mates, breeding grounds, and food. For female Ae. aegypti, that food is ideally human blood. But in a group of humans, what determines who gets bitten? Many people claim to be mosquito magnets, but Ellen De Obaldia admits she was skeptical when she joined Vosshall’s lab as a postdoc. It was only after she had designed the study and started getting results that she changed her mind. “Then, I truly believed it,” she says.

Previous work has shown that mosquitoes detect a suitable meal by sensing body heat, exhaled CO₂, and body odor. To determine what differences in body odor might account for mosquito preference, De Obaldia first needed some nylon stockings.

More than 60 volunteers wore nylons on their arms for 6 h to collect compounds from the skin. Then Vosshall’s team paired up nylons from different people and allowed mosquitoes to fly to their preferred sample. The researchers used the results from these head-to-head battles to build a ranking of mosquito magnets.

The team then extracted scent compounds from the nylons and analyzed them with gas chromatography/mass spectrometry. The team identified three fatty acids (pentadecanoic, heptadecanoic, and nonadecanoic acid) that correlated with mosquito preference, along with 10 other carboxylic acids that couldn’t be identified but were also alluring to the insects. The more of this scent mix that people produce on their skin, the more attractive to mosquitoes they are. Mutant mosquitoes that lack carboxylic acid receptors didn’t show the same preferences in the study.

Mosquito preference is a “central question” for researchers and the public, according to mosquito olfaction expert Marcus Stensmyr of Lund University. He says a strength of the study is that it repeated the tests with some of the same people a year later to show that their skin composition remained relatively constant, as did their attractiveness to mosquitoes.

What is unclear is whether mosquitoes use these compounds only to preferentially search out humans or if a combination of scents indicates that particular individuals might make better meals. That, Vosshall says, is a “super fascinating” question and means there is more of the perfume puzzle to uncover.

Stensmyr suggests that understanding the chemicals behind mosquito attraction could one day lead to a topical cream that could bring some relief for those on the tastier end of the mosquito magnet scale. But for now, Vosshall says the best advice she can give is to hang out with someone even more attractive to mosquitos. If a gathering of people is an all-you-can-eat mosquito buffet, she says, make sure there’s something more appetizing on the menu.