Have you ever wondered why some people seem to attract mosquitoes while others don’t? Well, a team of researchers from Virginia Tech recently discovered that certain soaps can actually make you more attractive or repellent to mosquitoes, depending on your unique odor profile. Interestingly, the same person who is highly appealing to mosquitoes when unwashed can become even more attractive with one soap, yet become repellent to them with another. The senior author and neuroethologist, Clément Vinauger, finds this phenomenon quite remarkable.
In order to investigate the correlation between the use of soap and attraction to mosquitoes, the scientists initially examined the chemical scents released by four individuals, before and after they washed themselves with four different soap brands- Dial, Dove, Native, and Simple Truth. The scent profiles of the soaps were also analyzed.
“Everybody smells different, even after the application of soap; your physiological status, the way you live, what you eat, and the places you go all affect the way you smell,” says co-author and biologist Chloé Lahondère (@Lahondere_Lab). “And soaps drastically change the way we smell, not only by adding chemicals, but also by causing variations in the emission of compounds that we are already naturally producing.”
The researchers conducted an experiment to determine the impact of various soaps on the attractiveness of human volunteers to Aedes aegypti mosquitoes. They tested the volunteers’ attractiveness to adult female mosquitoes who had recently mated, as male mosquitoes feed only on nectar. To eliminate the effect of exhaled carbon dioxide, they conducted preference trials on fabric that had absorbed the human volunteers’ odors instead of on the humans themselves. The results showed that the impact of soap-washing on mosquito preferences varied among soap types and human volunteers. While Dove and Simple Truth soaps increased the attractiveness of some volunteers, Native soap tended to repel mosquitoes.
“What really matters to the mosquito is not the most abundant chemical, but rather the specific associations and combinations of chemicals, not only from the soap, but also from our personal body odors,” says Vinauger. “All of the soaps contained a chemical called limonene which is a known mosquito repellent, but in spite of that being the main chemical in all four soaps, three out of the four soaps we tested increased mosquitoes’ attraction.”
“We know that ratios of chemicals are extremely important for determining whether mosquitoes are attracted or repelled,” says Lahondère. “Changing the ratio of the same exact chemicals can result in attraction, indifference, or repulsion.”
The researchers conducted an analysis of various soaps’ chemical compositions to identify the specific ingredients that attract and repel mosquitoes. They discovered four chemicals linked to mosquito attraction and three repellent chemicals, including a coconut-scented chemical used in American Bourbon and a floral compound used to treat scabies and lice. The team then combined these chemicals to create odor blends that were tested for their efficacy in attracting and repelling mosquitoes, yielding significant results.
“With these mixtures, we eliminated all the noise in the signal by only including those chemicals that the statistics were telling us are important for attraction or repulsion,” says Vinauger. “I would choose a coconut-scented soap if I wanted to reduce mosquito attraction.”
The team is aiming to further investigate these findings by conducting tests on a wider range of soap types and individuals. Additionally, they plan on exploring the impact of soap on mosquito preference over a longer duration. Vinauger expresses curiosity in studying the time course of this effect, such as whether taking a morning shower influences mosquito behavior in the evening.
