Could Your Soap Be Making You More Attractive to Mosquitoes?

A new study found that the type of soap a person uses may increase their risk of mosquito bites.

Mosquito bites can bring irritation and itching, as well as potential exposure to diseases carried by this insect with the long proboscis. If you find that mosquitoes tend to be drawn to you, it might be time to dive into the root cause of the issue, beginning with what you’re putting on your body to attract or deter the insect.

Researchers out of Virginia Tech examined whether or not some soaps worn by a person drew in or repelled mosquitoes. They found that soaps interact in interesting ways with a person’s natural olfactory signature—think of it as your own unique scent profile—impacting the chemical compounds that a mosquito responds to in a human host.

Lead author Clément Vinauger, PhD, assistant professor of biochemistry at Virginia Tech, told Health that soaps tend to be scented with chemicals that are associated with the pleasant scents of flowers found in nature. He said that mosquitoes also use “plant-emitted volatiles” to find flowers and get sugars from their nectar. With all of that in mind, he and his team expected that adding these floral-scented chemicals to soaps used for human hygiene would impact mosquitoes’ attraction to people.

“What was surprising in our results was the importance of the interaction between the specific soap chemicals and the body odor of each specific individual in determining whether a person would become more or less attractive to mosquitoes after applying soap to their skin,” Dr. Vinauger explained.

“In other words, we were surprised to see that some soaps, but not others, would increase the attractiveness of some people—but not others.”

Coconut as a Repellant

The study was relatively small—Dr. Vinauger and his team had four participants wash with soap from four brands, Dial, Dove, Native, and Simple Truth. These participants had both forearms rinsed for 30 seconds with deionized water and then dried with a paper towel.

One forearm would receive no further treatment, a nylon sleeve placed over it and wrapped in aluminum foil. Then they would wash the other forearm with the various soaps for 10-second periods and then rinse with the deionized water for another 10 seconds, followed by the nylon sleeve application and aluminum foil. The sleeves were used to capture the full smell from the skin that a mosquito could register, including one’s natural scent that would mix with the soap.

Separately, the soaps’ scents were examined on their own, with nylon sleeves washed with each soap and then rinsed off. Similar to the nylons applied to the participants’ forearms, clean sleeves rinsed with water, but without soap, were used as controls.

Following the scent collections, the sleeves were put in small cups which were then placed in a cage, where mosquitoes would ultimately be released to see which nylon drew—or repelled—the insects.

The mosquito species used in the study was Aedes aegypti, the main species that spreads diseases like Zika, dengue, and chikungunya.

All of the soaps featured limonene, which comes from citrus and is known to turn away mosquitoes. That ended up not mattering much. Three of the soap-washed sleeves attracted the mosquitoes, except for the Native-brand soap that contained a coconut scent.

“Remarkably, the scents of all the soaps were primarily dominated by limonene, known for its repellent effect on mosquitoes. In spite of this, three of the four tested soaps increased mosquito attraction,” Dr. Vinauger said, putting the findings into context.

“Our results indicate that more than the absolute amount of a given chemical, what really matters to the mosquitoes are the relative amounts of chemicals in mixtures.”

What Attracts Mosquitoes to People?

Dr. Vinauger explained that about 20% of human hosts are responsible for about 80% of mosquito-borne disease transmissions. Given that reality, he stressed how crucial it is for us to understand what makes a mosquito bite one person over another.

“While other studies have determined which chemicals among those we produce as part of our body odor attracts mosquitoes, the effect of smells we routinely add to our odor remained to be determined,” he added.

Patrick “PJ” Liesch, MS, is the director of the UW-Madison Insect Diagnostic Lab, and “the Wisconsin Bug Guy” who regularly gives talks and media appearances about all things insects. Liesch, who is unaffiliated with this new study, told Health that mosquitoes can be drawn to people for a range of reasons.

“Volatile chemicals associated with the skin can play an important role at closer distances, and can help explain some of the noticeable differences in attractiveness from person to person,” he explained. “Everyone differs in their unique odor caused by volatiles on the skin, and this can be influenced by factors such as genetics, age, gender, metabolism, diet, exercise, personal care routines, and the microbiome of our skin.”

When it comes to the new study, Liesch said that “soap chemistry is complex”—each type of soap can differ in chemical composition and also in the shifts it causes “in skin volatiles after use.”

“The researchers in the recent paper did find that very specific chemicals happened to increase or decrease attractiveness to one species of mosquito, although the exact reason isn’t fully understood in many cases,” he noted.

Protecting Yourself From Mosquitoes

Liesch said “it’s too early to tell” if studies like this one can tell someone how to best protect themself from mosquito bites. He added that this research into soaps and how they impact mosquito attraction “is fascinating,” but more needs to be done before we can determine if we should make changes to our personal care routines.

“With approximately 3,600 mosquito species known worldwide, additional testing would be needed,” Liesch explained. “Nonetheless, the study does demonstrate that our personal care routines can influence volatiles on our skin, which may impact our overall attractiveness to mosquitoes.”

He suggested a few things people can do to avoid mosquitoes, aside from purchasing different soaps. Most importantly, avoid places with high mosquito activity. You might want to change your outdoor activities and spend time on a screened-in porch, for example. You could also set up fans if you’re having a summer party outside in your backyard to create air movement that might disperse the insects.

“With their small body mass, mosquitoes may struggle to reach you if you’re sitting near a fan. Additional options include wearing long-sleeved clothing to prevent mosquitoes from getting to skin, and using EPA-registered repellents such as DEET, picaridin, IR3535, or oil-of-lemon eucalyptus,” he said. “Managing vegetation and standing water in your yard can also be important ways to reduce local mosquito populations in your yard.”

Looking Ahead

Liesch noted two key takeaways. First, we really don’t fully understand all of the factors that are in play when it comes to mosquitoes’ attraction to humans. We don’t know whether altering our personal care routine could change how a mosquito responds to us. Additionally, he said that research like this could play a big role in developing newer, better mosquito repellents down the line.

For Dr. Vinauger, the new study offers “proof of concept that soaps interact with our body odor.” That being said, he and his team are seeking funding to add more volunteers and more types of soap to gain “a better understanding of the chemical processes at play.”

“The next big question for us is how long do these effects last?” he said. “If I take my shower in the morning, does it still matter for the mosquitoes that I will encounter in the late evening?”