You may have noticed that not everyone gets bitten by mosquitoes. Scientists have long known that different people attract pests at different rates, but they have failed to explain why some people are "mosquito magnets" while others avoid getting bitten.
Researchers propose that specific body scents are the decisive factor in a recent work that was published on October 18 in the journal Cell. The researchers discovered that mosquitoes were more drawn to people whose skin produced large levels of carboxylic acids, which each person's individual fragrance profile is made up of. In addition, the researchers discovered that despite dietary or grooming routine changes, people's attractiveness to mosquitoes remained constant over time.
Leslie Vosshall, co-author of the study and a neurobiologist at the Howard Hughes Medical Institute and Rockefeller University who specialises on mosquitoes, claims that “everyone asks the question of why some people are more attractive to mosquitoes than others.”
Scientists have proposed several hypotheses to explain why some of us are targeted by mosquitoes more frequently than others, including the notion that variations in blood types must be at play. Vosshall notes that the evidence is scant for this connection. Over time, scientists came to agree on the hypothesis that body odour must be the main factor attracting mosquitoes. But researchers have been unable to determine the particular smells mosquitoes favour.
Vosshall and her coworkers gathered 64 individuals and asked them to wear nylon stockings on their arms to test their hypothesis. The nylons were infused with each person's own scent after six hours. According to Maria Elena De Obaldia, a senior scientist with the biotech company Kingdom Supercultures and the principal author of this new study, which she did while at Rockefeller University, "Those nylons would not have a scent to me or, I suppose, to anyone truly." The stockings were still definitely offensive enough to draw insects.
Two nylons, each from a different person, were cut into pieces by the researchers and put into a container with female Aedes aegypti mosquitoes. Did they all move to subject number one's sample or did they favour subject number two's scent? Or did both appeal to you equally? According to Vosshall, the researchers carried out these head-to-head contests over a period of months, obtaining additional samples from the individuals as required. The team had concrete evidence indicating some people were more beautiful than others when the competition was over. According to the study's authors, Subject 33 had the unfortunate distinction of being the biggest mosquito magnet because their beauty score was "almost 100 times greater" than those of the least attractive individuals, 19 and 28.Although the amount varies from person to person, humans release carboxylic acids at far higher amounts than the majority of animals. There were insufficient individuals in the new study to determine which personality traits increase the likelihood of producing high levels of carboxylic acids, and there is no simple technique to test your own skin's carboxylic acid levels without a laboratory.
However, we are aware that over time, the level of carboxylic acids in skin remains largely stable. Consequently, an even odour profile results. (According to Vosshall, mosquitoes might also be drawn to skin microorganisms that break down the carboxylic acids we make.) Vosshall and De Obaldia discovered that people's attractiveness rankings stayed roughly the same when they repeated their tournament several times over several months. It didn't seem to matter what each individual ate or what brand of soap they used, or any other personal aspects that might have altered over those months.
According to who you are, "this attribute of being a mosquito magnet persists with you for your entire life—which is either good news or bad news," says Vosshall.
Omar Akbari, a cell and molecular biologist at the University of California, San Diego, who was not involved in the study but whose recent work focuses on mosquitoes, says that the study "confirms, in a very careful way, that it is true that some people are more attractive [to mosquitoes] than others." He continues by saying that the discovery in the study of particular carboxylic acids as a significant factor in mosquito attractiveness is a brand-new insight into how insects behave.
According to Akbari, the findings of this study, which concentrated on Aedes aegypti mosquitoes, are likely generalizable to other mosquito species that also primarily prey on people.
However, all is not lost if you believe you might attract mosquitoes. The findings, according to Akbari, might aid scientists in the future creation of more potent insecticides. The secret may be in changing the skin's odour profile by introducing new bacteria to the microbiome already present there.
However, there is still one lingering query: Why do mosquitoes adore the aroma of carboxylic acids or the accompanying microorganisms so much? De Obaldia has a response for that, but she admits it's a little hypothetical. She points out that A. aegypti mosquitoes have evolved specifically to prey on people (possibly because we often have containers of clean water nearby, which is a perfect breeding place for them). As a result, A. aegypti mastered the ability to distinguish between the smell of humans and other animals. Humans produce large amounts of chemicals called carboxylic acids, but other species do not. So, according to De Obaldia, because carboxylic acids are a great sign that a someone is nearby, mosquitoes presumably developed a fondness for them.
If you see that you have more bites than all of your friends combined, you can find comfort in the knowledge that mosquitoes like your fragrance because it is so obviously human.
