Why mosquitoes prey on some people and pass on others remains a mystery, although many studies point to the smell that humans give off. Now, a new study suggests that the aroma of a soapcombined with the personal odor of some individuals, it can attract or repel mosquitoes.

The detailed studies, carried out by scientists of the Virginia Polytechnic Institute and State University (Virginia Tech)are published this wednesday in the magazine ‘iScience’.

Research has found that an individual, extremely attractive to mosquitoes when unwashed, «can become even more attractive for mosquitoes with a soapand become repulsive to mosquitoes with another,» summarizes the lead author and neuroethologist Clément Vinauger.

plant nectar

the mosquitos does not feed only on blood. In fact, its main source of food is the plant nectarso using aromas derived from plants or that imitate them could influence your decision.

To find out, the team characterized the chemical odors emitted by four unwashed volunteers and after washing themselves with four marks of soap: Dial, Dove, Native and Simple Truth.

They also characterized the odor profiles of the soaps.

odor profiles

They found that each volunteer emitted their own odor profile, some more attractive to mosquitoes than others, and that the use of soap significantly changed these. odor profiles.

«Everybody smells different, even after applying soap; your physiological state, your way of life, what you eat and the places you go to disappear to the way you smell,» he explains. Chloé Lahondère, biologist and study co-author.

«And soaps necessarily change our form of oil, not only by adding chemicals, but also by causing variations in the emission of compounds that we already produce naturally,» he details.

before and after soap

The researchers compared the attractiveness of each volunteer to mosquitoes. Aedes aegypti without washing and an hour after using the soaps and always with female mosquitoes, which feed on blood after appearing with the males.

The experiment revealed that soap washing influenced mosquito preferences, but in different ways for different types of soap and volunteers.

Washing with Dove and Simple Truth increased the attractiveness of some volunteers (not all), and washing with Native soap tended to mosquito repellent.

«What really matters to the mosquito is not the most abundant chemical, but the specific associations and combinations of chemicals, not just in soap, but also in our personal body odorsVinauger says.

In fact, although all four soaps contained limonene -a well-known natural repellent-, three of them increased the attraction of mosquitoes.

And it is that «the proportions of the chemical substances are extremely important to determine if the mosquitoes are attracted or not,» Lahondère added.

Coconut scent for repeller

The next step was to analyze the chemical compositions of the different soaps based on their impact on mosquito preference.

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Thus, they identified four chemical substances associated with mosquito attraction and three associated with repulsion, among the latter a coconut-scented chemical that is a key component of mosquitoes. american bourbon and a floral compound used to treat scabies and the lice.

The team intends to expand on these results and find some patterns or rules of thumb by testing more varieties of soap and using more volunteers, and also plans to study how long a soap lasts for hours.