The body wash you use in the shower may react with your natural odour to make you more attractive to mosquitoes.
Mosquitoes use various methods to find a target for their next blood meal, such as detecting an animal’s body heat, odour and the carbon dioxide they emit.
To learn if the body wash we use may have an effect, Clément Vinauger at Virginia Polytechnic Institute and State University and his colleagues selected varieties from the brands Dial, Dove, Native and Simple Truth.
First, they placed two strips of nylon on one of the forearms of four volunteers and wrapped that area in foil, to collect the participants’ natural odour.
Next, the researchers washed part of each participants’ other forearm with about 1 gram of one of the body washes for 10 seconds, before rinsing it with water for a further 10 seconds. They then similarly applied two strips of nylon and foil to these forearms, to collect the wash’s scent. The researchers repeated this with the three other body washes.
One hour after each sample was taken, they took two strips – one from each of the body wash-exposed areas and one from the body wash-free areas – for chemical analysis while the other body wash-free and body wash-exposed strips were put in separate cups.
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The researchers placed these inside cages with 16 to 25 female Aedes aegypti mosquitoes, which can transmit yellow fever, that were free to visit either cup.
The Simple Truth body wash appeared to increase the attractiveness of all of the participants, measured by the number of times the mosquitoes landed on their body wash-exposed strips compared with their body wash-free strips. The Dove wash had a similar effect, but the increase in attractiveness was only pronounced for three of the participants.
Dial’s body wash similarly made the participants more attractive to mosquitoes, but to a lesser extent than Simple Truth’s or Dove’s.
In contrast, the mosquitoes tended to avoid the strips washed in the Native body wash, but displayed a particularly strong aversion towards one participant’s Native-washed strip.
This suggests the body washes’ fragrances and the participants’ individual odours combined to create a scent that was detectable to the mosquitoes.
“Our study highlights the importance of the interaction between the specific soap chemicals and the body odour of each person in determining whether a person would become more or less attractive to mosquitoes after applying soap to their skin,” says Vinauger.
The experiment’s chemical analysis suggests that the compounds benzaldehyde, benzyl benzoate and γ-nonalactone may repel mosquitoes.
The researchers are planning to repeat their study with a larger group of participants and more body washes, and will investigate how long a wash’s potential mosquito-attracting or mosquito-repelling effects last after it is washed off the skin.
“The discovery that personal care products may cause mosquitoes to be attracted or repelled by the user opens the door for developing user-friendly mosquito repellents,” says Walter Leal of the University of California, Davis.
“The chemicals in such products may not directly affect mosquito behaviour, but they may disrupt the specific ratio of human emissions that attract mosquitoes,” he says. “Regardless of the mechanism, reducing human-mosquito interactions mitigates the transmission of vector-borne diseases.”
New Scientist contacted the four body washes’ manufacturers for comment but received no reply prior to publication.
iScience DOI: 10.1016/j.isci.2023.106667