The arena featured a ring of landing pads heated to human skin temperature (35ºC). Each night, 200 hungry mosquitoes were released into the arena, and their movements were tracked using infrared cameras. The researchers specifically observed how often the mosquitoes landed o­n each pad, which indicated their readiness to bite.

Initially, the team compared the relative importance of heat, CO2, and human body odor in attracting mosquitoes. They found that mosquitoes were o­nly drawn to the heated landing pads when they were also baited with CO2, but human body odor was even more attractive than CO2 alone.

To test the mosquitoes' selectivity, the researchers had six individuals sleep in single-person tents surrounding the arena for six consecutive nights. Air from each tent, containing the occupant's scent, was channeled o­nto the heated landing pads via repurposed air conditioner ducts. In addition to recording the mosquitoes' preferences, the researchers collected air samples from the tents each night to analyze and compare the airborne components of body odor.

These mosquitoes typically hunt humans between 10 PM and 2 AM, following scent trails and currents from humans. The researchers aimed to evaluate mosquito olfactory preferences during this peak activity period and assess the odors emitted by sleeping humans during the same window.

Night after night, the researchers observed that some individuals were consistently more attractive to mosquitoes than others. o­ne volunteer, whose odor composition was markedly different from the others, attracted very few mosquitoes.

The team identified 40 chemicals emitted by all the participants, but in varying amounts. "It's likely a specific blend of ratios they're following," explained analytical chemist Stephanie Rankin-Turner, another lead author of the study. "We don't yet know exactly which aspects of skin secretions, microbial metabolites, or breath emissions are driving this, but we hope to figure that out in the coming years."

Although each person's odor profile varied from night to night, the researchers identified some consistent patterns. Those who were more attractive to mosquitoes emitted higher levels of carboxylic acids, likely produced by skin microbes. In contrast, the least attractive person emitted lower levels of carboxylic acids but about three times more eucalyptol, a compound found in many plants. The researchers hypothesize that elevated eucalyptol levels may be related to this person's diet.

The researchers were surprised by how effectively the mosquitoes could locate and differentiate between potential human hosts in such a large arena. "When you take something from a small laboratory setting where the odors are concentrated and see mosquitoes still finding them in this vast open space in Zambia, it really emphasizes how powerful these mosquitoes are as host seekers," said Rankin-Turner.

This research was funded by the Johns Hopkins Malaria Research Institute, Bloomberg Philanthropies, and the Human Frontier Science Program.

Are you a magnet for mosquitoes? Relief might be o­n the way

As summer begins, I o­nce again experience the annual transformation from human to a living pincushion. Whether at home or abroad, when mosquitoes are o­n the hunt, I'm reminded by a blanket of red welts?some swelling to the size of golf balls?that my blood is irresistible to them. During a tropical Christmas vacation last December, a day that started with a barrage of mosquito bites quickly turned into a painful experience when I was also stung by jellyfish and wasps. At this point, I can o­nly assume mosquitoes are inspiring other species to target me.

But there is hope for the 20% of the population who receive an above-average number of mosquito bites. Earlier this month, researchers at the Hebrew University of Jerusalem (HUJI) developed a new repellent that could reduce mosquito bites by 80%. A thin layer of naturally occurring cellulose nanocrystals (CNC) combined with indole, an organic compound with a pungent odor, applied to the skin acts as "chemical camouflage," according to a study published in PNAS Nexus. This combination disrupts the signals mosquitoes use to identify their victims and is considered "unprecedented," according to Jonathan Bohbot, a senior lecturer at HUJI and o­ne of the study's co-authors. The results are so promising that further human trials are planned, with the goal of gaining regulatory approval for commercial use. Bohbot notes that this CNC-repellent combo could be more effective and longer-lasting than current products o­n the market, with high adoption rates expected if it becomes available.

Whether you get bitten or not is largely predetermined; some estimates suggest that genetics account for 85% of a person?s likelihood of being bitten. DNA testing company 23andMe has identified 285 genetic markers responsible for the frequency, itchiness, and size of mosquito bites.

Mosquitoes are drawn to humans by volatile organic compounds in our breath, but it's the chemicals we release through our skin, like lactic acid and ammonia, that guide them to feed. The more lactic acid your body produces, the more intense the feeding frenzy. Since altering our physiology is not an option, repellents remain our primary defense?a market projected to reach $9 billion by 2026.

HUJI?s researchers aren?t the o­nly o­nes working o­n a solution. Earlier this year, Italian scientists developed a repellent combining cyclic acetals and carbonyl compounds that is reportedly four times more effective than DEET, the active ingredient in many sprays and creams. Tested against the tiger mosquito, Aedes albopictus, it protected 95% of people for up to eight hours (compared to two hours with DEET) and was less toxic and odorous than current options. Published in the Journal of Agricultural and Food Chemistry, this formula could be a welcome addition to the market. ?We didn?t think it was that easy to find a new repellent,? said Francesca Dani, associate professor of zoology at the University of Florence, adding that her team was ?pretty satisfied? with the results.

The team?s next goal is to test whether their repellent can protect against other pests like ticks, which have been linked to tick-borne encephalitis, a potentially fatal virus recently found in the UK, and Anopheles gambiae, the mosquito species that spreads malaria. Repellents are "the o­nly way you can keep disease vectors away," Dani says. "It's a very simple way to protect people."

While being bitten is o­ne of the more minor issues mosquitoes cause, repellents do little to combat diseases like malaria. Ancient civilizations relied o­n remedies like vinegar or burnt snakeskin to deter mosquitoes, but chemical solutions o­nly became available in 1957 with the introduction of DEET. Although DEET is effective, its toxicity limits its concentration in products sold in the UK and Europe. Icaridin, IR3535, and citriodiol are popular alternatives, but none have yet achieved the perfect balance of effectiveness, odorlessness, non-toxicity, and resistance to water and grease.

Your propensity to being bitten by mosquitoes - as well as to itching and swelling - seems to be determined by genetics. Photograph: kmatija/Getty Images