This is why mosquitoes are more attracted to some people than others

(CNN) — If you’ve always suspected you’re just a mosquito magnet, scientists now have proof for you: Mosquitoes are actually more attracted to certain people than others, according to a new study.

A research team led by Leslie Vosshall, a Rockefeller University professor and head of her Laboratory of Neurogenetics and Behavior, was trying to figure out why certain people seem to attract more mosquitoes than others. The research results were published in the journal Cell on October 18.

Over the course of three years, the researchers asked a group of 64 volunteers to wear nylon stockings on their arms for six hours a day for several days. Maria Elena De Obaldia, the study’s first author and former postdoctoral fellow at Rockefeller University, constructed a “two-choice olfactometer assay” — an acrylic glass chamber into which the researchers placed two of the stockings. The study team then released yellow fever mosquitoes, scientifically called Aedes aegypti, into the chamber and observed which sock attracted more insects.

This test allowed the researchers to separate study participants into “mosquito magnets,” whose stockings attracted many mosquitoes, and “low attractors,” which didn’t seem as enticing to the insects. The scientists examined the skin of the mosquito magnets and found 50 molecular compounds that were higher in these participants than the others.

“We didn’t have any preconceived notions about what we were going to find,” Vosshall, who is also the scientific director of the Howard Hughes Medical Institute, told CNN. But one difference was particularly striking: the mosquito magnets had much more carboxylic acid on their skin than the low-level attractors.

Carboxylic acids are found in sebum, the oily substance that forms a barrier and helps keep our skin hydrated.

The carboxylic acids are large molecules, explained Vosshall. They’re “not that smelly on their own,” she said. But beneficial bacteria on the skin “chew on those acids that create people’s signature odor” — which Vosshall says could attract mosquitoes.

Odor of skin secretions play a role

One participant, identified only as subject 33, was the prom queen for mosquitoes: the subject’s stockings were 100 times more attractive to mosquitoes than the least attractive participants.

And attraction to people seemed to remain fairly constant over time for the participants monitored over the three-year period, Vosshall said.

Subject 33, for example, “never took a day off to be the most attractive person,” which could be “bad news for mosquito magnets.”

When it comes to Aedes aegypti, female mosquitoes prefer human blood to fuel their egg production, making their search for humans to prey more urgent. And these mini-predators use a variety of mechanisms to identify and select the people they bite, Vosshall said.

Carboxylic acids are just one piece of the puzzle to explain how the pesky insects might choose their targets. Body heat and the carbon dioxide we release when we breathe also attract mosquitoes.

Scientists still don’t know why carboxylic acids attract mosquitoes so strongly, Vosshall said. However, the next step could be to study the effects of reducing carboxylic acids on the skin.

“You can’t completely remove natural moisturizers from your skin, that would be bad for your skin health,” she said. However, Vosshall said dermatological products may be able to minimize carboxylic acid levels and reduce mosquito bites.

“Any bite from these mosquitoes puts people at risk for public health,” she said. “Aedes aegypti mosquitoes are vectors for dengue, yellow fever and Zika. People who are magnets are much more likely to get infected with viruses.”

Mosquitoes have evolved to hunt by scent

Matthew DeGennaro, an associate professor at Florida International University who specializes in mosquito neurogenetics, told CNN that the study’s findings help answer longstanding questions about what specific factors make mosquitoes love some people more than others. He was not involved in the study.

“This study clearly shows that these acids are important,” he said. “Now how the mosquitoes perceive these carboxylic acids is interesting because these particular chemicals are really heavy, so it’s hard to smell them from afar.

“It could be that these chemicals are altered by the skin’s microbiome, for example, and cause a certain type of odor trail. Or it could be that other factors in the environment break down those chemicals a bit, so they’re easier for mosquitoes to spot.”

The results are also “a really great example of how good insects can smell,” DeGennaro added. “This insect evolved to hunt us.”

For DeGennaro, one of the most interesting aspects of research is the persistence of attractiveness in certain people.

“We didn’t know that there were very stable mosquito preferences for certain people,” he said. “It might suggest that the skin microbiome is important, although they didn’t address that.”

Further research should examine the microbiome that lives on human skin to understand why mosquitoes are attracted to certain compounds over others, he said. And that could lead to better products to reduce mosquito bites and the spread of disease.

“I think if we understand why mosquitoes find a host, we can design new repellents that block the mosquitoes from sensing these chemicals,” DeGennaro said. “And this could be used to improve our current defenses.”