Soap can make you more or less attractive to mosquitoes

For centuries, people have wondered why some individuals seem to be irresistible to mosquitoes while others manage to escape their bites unscathed. 

A group of scientists from Virginia Tech may have discovered a clue to this enigma. In a study published in the journal iScience, researchers found that the use of certain soaps can either attract or repel mosquitoes, but these effects depend on the unique odor profile of each person.

“It’s remarkable that the same individual that is extremely attractive to mosquitoes when they are unwashed can be turned even more attractive to mosquitoes with one soap, and then become repellent or repulsive to mosquitoes with another soap,” said study senior author Clément Vinauger.

Since ancient times, humans have utilized soaps and perfumed personal products to alter their body odor. These products are known to change our perception of one another’s scent, but it remains unclear whether they also affect how mosquitoes perceive and discriminate between potential blood donors. 

As mosquitoes primarily feed on plant nectar, using plant-derived or plant-mimicking scents could potentially confuse their decision-making process.

How the study was done

To investigate the connection between soap usage and attractiveness to mosquitoes, the research team first analyzed the chemical odors emitted by four human volunteers, both before and after washing with each of four different soap brands—Dial, Dove, Native, and Simple Truth. Additionally, the odor profiles of the soaps themselves were characterized.

The study revealed that every volunteer had their own distinct odor profile, with some being more appealing to mosquitoes than others. Washing with soap significantly altered these odor profiles, and the changes were not solely due to the addition of floral fragrances.

“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. 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,” explained study co-author Chloé Lahondère.

Washed vs. unwashed

The researchers focused on Aedes aegypti mosquitoes and compared the relative attractiveness of each human volunteer before and after washing with various soaps. 

To ensure accurate results, they exclusively tested adult female mosquitoes who had recently mated, as only these mosquitoes feed on blood. Additionally, the team conducted the experiments on fabric infused with the volunteers’ odors, eliminating the effects of exhaled carbon dioxide (CO2), another crucial cue for 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,” said Vinauger.

Interestingly, despite all the soaps containing limonene, a known mosquito repellent, three out of the four soaps tested actually increased mosquitoes’ attraction.

“We know that ratios of chemicals are extremely important for determining whether mosquitoes are attracted or repelled. Changing the ratio of the same exact chemicals can result in attraction, indifference, or repulsion,” said Lahondère.

Identifying specific ingredients

To pinpoint the specific ingredients that attract or repel mosquitoes, the researchers analyzed the chemical compositions of the different soaps in relation to their impacts on mosquito preference. 

They identified four chemicals linked to mosquito attraction and three chemicals associated with repulsion, including a coconut-scented chemical found in American Bourbon and a floral compound used to treat scabies and lice. 

The team then combined these chemicals to create and test attractive and repellent odor blends, which significantly influenced mosquito preference.

Vinauger suggested, “I would choose a coconut-scented soap if I wanted to reduce mosquito attraction.”

The researchers aim to build on these findings by testing more soap varieties and a larger number of volunteers to identify general patterns or rules. They also plan to investigate how soap impacts mosquito preference over an extended period. 

Vinauger expressed curiosity about the longevity of the effect: “If you take a shower in the morning, does it still matter to mosquitoes in the evening?”

This groundbreaking research highlights the complex interplay between soap usage, individual odor profiles, and mosquito attractiveness. Further studies could help develop personalized strategies for reducing the risk of mosquito bites, and in turn, the transmission of mosquito-borne diseases.

More about mosquitoes

Mosquitoes have long been a source of annoyance for humans due to their bites and persistent buzzing. However, their impact on humanity and the environment goes far beyond mere irritation. Mosquitoes play a significant role in the transmission of various deadly diseases, making them one of the most dangerous creatures on Earth.

Impact on Humanity:

Disease transmission

Mosquitoes are vectors for numerous diseases that affect millions of people worldwide. Some of the most devastating mosquito-borne illnesses include malaria, dengue fever, Zika virus, West Nile virus, chikungunya, and yellow fever. Malaria alone is responsible for over 400,000 deaths per year, primarily affecting children under five years old in sub-Saharan Africa.

Economic burden

The cost of treating and preventing mosquito-borne diseases places a substantial economic burden on affected countries, particularly in the developing world. The expenses associated with medical care, vector control programs, and lost productivity due to illness can strain already limited resources.

Social impact

Mosquito-borne diseases can hinder social and economic development in affected regions. High disease prevalence may lead to reduced educational opportunities, decreased workforce productivity, and increased poverty.

Impact on the Environment:

Biodiversity

Mosquitoes are a vital part of many ecosystems, serving as a food source for various organisms such as birds, bats, and fish. They also play a role in pollination, helping to maintain plant diversity.

Ecosystem balance

Mosquito larvae are primary consumers in aquatic ecosystems, feeding on organic matter and microorganisms. They help recycle nutrients and contribute to the food chain, supporting the existence of other species.

Control measures and their consequences

Efforts to control mosquito populations often involve the use of insecticides, which can have unintended consequences on the environment. These chemicals may harm non-target species, contaminate water sources, and lead to pesticide resistance in mosquito populations. Additionally, the release of genetically modified mosquitoes or the use of other biological control methods may carry unforeseen ecological risks.

In conclusion, mosquitoes have a complex relationship with humanity and the environment. While they play essential roles in ecosystems and contribute to biodiversity, they also pose significant threats to human health and well-being. Managing mosquito populations and mitigating the spread of mosquito-borne diseases are critical challenges that require ongoing research, innovation, and global cooperation.

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