“It’s a very simple way to protect people.” Being bitten is among the more minor issues caused by mosquitoes. Repellants are “the only way you can keep vectors away”, says Dani. Those currently in their sights are ticks (health officials warned last month that tick-borne encephalitis, a virus that can be fatal, had been found in the UK) and Anopheles gambiae, the mosquito species responsible for spreading malaria. The team’s next goal is to see whether their repellant can ward off other pests, too. “We didn’t think it was that easy to find new repellant,” says Francesca Dani, associate professor of zoology at the University of Florence, adding: “We were pretty satisfied.” The results, published in the Journal of Agricultur al and Food Chemistr y, could make it another welcome addition to the market. Tested against the tiger mosquito, Aedes albopictus, it was found to protect 95% of people for eight hours at a time (DEET lasts for about two) and is a less toxic and odorous blend than those currently available. Earlier this year, a group of Italian scientists developed a repellant combining cyclic acetals and carbonyl compounds, creating a formula they say is four times as effective as DEET (diethyltoluamide, the chemical compound that makes up a large tranche of sprays and creams). HUJI’s researchers aren’t the only ones looking to solve the bite problem. Given the limitations in changing our physiology, repellants are, for now, really the only defence we have – bought across the globe in such numbers that the market is predicted to reach $9bn (£7.2bn) by 2026. The more lactic acid your body produces, the worse the feeding frenzy is likely to be.
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But it is those we release through our skin that serve as signposts to where they should feed from chemicals we naturally produce, such as lactic acid and ammonia. Mosquitoes are attracted to humans by volatiles (organic compounds) we emit in our breath. Whether you get bitten or not is, in large part, a foregone conclusion: by some estimates, genes account for 85% of a person’s propensity to be stung, while DNA testing company 23andMe says it has identified 285 heritable genetic markers responsible for their frequency, itchiness and size.
“The CNC-repellant combination will have a longer efficacy and range of action than other products currently available on the market,” says Bohbot, adding that they expect “high levels of product adoption” if and when it does hit shelves. Indeed, the results are considered so promising that further human studies are planned, with a view to having the coating approved by regulators ahead of commercial use.
This combination – which derails the cues that mosquitoes use to select their victims – is “unprecedented”, according to Jonathan Bohbot, a senior lecturer at HUJI and one of the paper’s co-authors. Applying a thin coating made from naturally occurring cellulose nanocrystals (CNC), a renewable raw material found in the likes of cotton and wood, and indole, an organic compound with an unpleasant odour, to skin served as “chemical camouflage”, said the study published in PNAS Nexus.
Earlier this month, researchers at the Hebrew University of Jerusalem (HUJI) developed a new repellant capable of reducing the number of mosquitoes feeding by 80%. At this point, I can only assume the mosquitoes are giving other species ideas.īut there are signs that a solution for the 20% of the population who receive above-average numbers of bites may soon be at hand. On a single day last December, a tropical Christmas trip quickly became a less-than-festive scratchathon after a glut of bites arrived, following which I was stung by jellyfish, then wasps. Whether at home or abroad, when mosquitoes begin their hunt for blood I am reminded, via a blanket of red blotches that have more than once swelled to the size of a golf ball, that mine is a godlike nectar. T he earliest signs of summer herald my annual metamorphosis – from woman to lifesize pincushion.
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