Why are you always covered in mosquito bites while others escape untouched? Scientists uncover the hidden skin chemistry that may make some people irresistible to mosquitoes

Some people can spend an evening outdoors and barely notice a mosquito. Others can return indoors covered in itchy red bumps, wondering why the insects seemed to single them out. For years, scientists have known that mosquitoes do not bite every person equally. But a new study suggests there may be an even more complicated reason for that difference: the answer could partly lie in the unique chemical “signature” of a person's skin.

Researchers found that three mosquito species linked to human disease did not necessarily prefer the same people. Instead, each species appeared to respond to different combinations of skin odours and bacteria.

The findings, published in iScience, could eventually help scientists develop mosquito traps and repellents that are designed for particular species rather than treating all mosquitoes as though they behave in the same way.

Your skin is giving off a chemical signal

To a human nose, skin may simply smell like skin. To a mosquito, it is far more complicated. Scientists have found that mosquitoes use several clues when searching for a host, including smell, body heat, humidity, carbon dioxide from breathing and visual cues. Once they get close, chemicals released from the skin can help them decide where to land and feed.

And much of that smell does not come directly from human cells. Bacteria living naturally on the skin break down substances found in sweat and skin oils and turn them into volatile chemicals that enter the surrounding air. Those chemicals become part of each person's distinctive body odour. Because people's skin microbiomes differ, their chemical scent profiles can differ too.

That may help explain why one person can appear to be a mosquito magnet while someone sitting nearby escapes almost untouched.

Researchers put three mosquito species to the test

Matthew DeGennaro, a neurogeneticist at Florida International University, and his colleagues recruited 119 volunteers for the experiment. They tested three species: Aedes aegypti, Aedes albopictus and Culex quinquefasciatus. All are capable of transmitting diseases, although their behaviour and preferred feeding times differ.

For the two Aedes species, volunteers placed an arm into a specially designed device. The mosquitoes could detect the person's smell but could not actually bite them.

Culex quinquefasciatus is primarily active at night, so the researchers used a different approach. Volunteers wore nylon sleeves for several hours, allowing the material to collect their scent. The sleeves were then placed in the testing apparatus in darkness.

The researchers counted how many mosquitoes moved towards each person's scent.

The surprising part: mosquitoes did not agree on their favourite people

The results showed that the three species had different preferences. Some volunteers were particularly attractive to one mosquito species but not another. A person who appeared highly appealing to one species was not automatically attractive to the others.

The researchers also found that Aedes aegypti showed a small but statistically meaningful preference for male volunteers in this experiment.

Most strikingly, no volunteer strongly attracted all three mosquito species. That suggests the familiar idea that someone is simply “more attractive to mosquitoes” may be incomplete. A person's attractiveness may depend on which mosquito species is doing the choosing.

What is happening on the skin?

The researchers collected samples of the airborne chemicals around volunteers' arms and examined bacteria living on their skin. They found that Aedes aegypti and Culex quinquefasciatus tended to be more attracted to people whose overall skin odour was weaker.

Aedes albopictus, meanwhile, was associated with 13 chemicals that have plant-like odours.

The scientists also noticed several bacterial species among people who were particularly attractive to all three mosquito species. These included Corynebacterium kefirresdentii, Cutibacterium granulosum and a strain of Staphylococcus epidermidis.

But that does not mean having one of these bacteria automatically makes someone more likely to be bitten. Human body odour is an extraordinarily complicated mixture, and researchers cannot yet identify every chemical involved or explain exactly how different bacterial communities alter mosquito behaviour.

Why this matters beyond itchy bites

The research could eventually have implications for disease prevention.

Mosquitoes are not merely irritating insects. Species such as Aedes aegypti can transmit dengue, chikungunya and yellow fever, while other mosquitoes can spread diseases including West Nile virus.

Previous research has already established that differences in human skin bacteria and odour can influence mosquito attraction. Studies have also identified individual chemicals that can either draw mosquitoes towards people or make them less attractive.

The new findings add another layer: different mosquito species may be reading different chemical signals from the same human skin.

That raises the possibility of developing more targeted approaches. Instead of creating one universal mosquito repellent, scientists could potentially design chemicals or microbial treatments that interfere with the particular scent cues used by a specific species.

Researchers also envision using attractive scents in traps, effectively drawing mosquitoes away from people.