Why Do Mosquitoes Keep Choosing the Same People?

Mosquitoes do not experience every human as equally attractive. To a mosquito following scent, some people consistently stand out from the crowd.

Researchers at Rockefeller University asked participants to wear nylon sleeves on their forearms, allowing the fabric to collect chemicals released by their skin. The sleeves were then placed inside a testing chamber with female Aedes aegypti mosquitoes. When samples were matched against one another in repeated contests, certain people attracted far more mosquitoes than others.

These differences remained remarkably stable over several years. Chemical analysis found that the most attractive participants had higher levels of particular carboxylic acids in the substances emanating from their skin. Humans naturally produce these acids in sebum, and microorganisms living on the skin may influence the resulting odor mixture.

This does not mean that one chemical completely determines who gets bitten. Mosquitoes combine several signals, including carbon dioxide from breathing, body heat, moisture, visual contrast, and numerous odors. Different mosquito species may also respond differently. The Rockefeller study examined attraction primarily in Aedes aegypti, a species that specializes in feeding on humans.

Common explanations involving sweet blood or recently eaten foods are therefore too simple. Much of the answer exists outside the bloodstream, in an invisible chemical cloud surrounding the skin.

A person who repeatedly becomes the group’s mosquito magnet may not be imagining it. To the mosquito’s sensory system, that individual may carry a recognizable and unusually attractive scent for years.