By Jodi Helmer, AARP July 2023
Repelling Mosquitoes: What Science Says Does and Doesn’t Work. Here's some unexpected ways to get biting insects to buzz off. Nothing ruins an outdoor adventure faster than ravenous mosquitoes.
The biting insects are a big downer in the summer months — and things could get worse. Mosquito populations are increasing and expanding their range, according to 2019 research published in the journal Nature Microbiology, leaving more people vulnerable to bites that cause red bumps and itchy skin. Mosquitoes can transmit serious diseases around the world, including West Nile virus, Zika and malaria.
Though malaria is not often found in the United States, the Centers for Disease Control and Prevention (CDC) issued a health alert around mosquitoes and malaria. The CDC recently identified four cases of malaria in Florida and one in Texas in people who appear to have been exposed to the disease locally. Doctors and public health officials should be on the lookout for increased cases as people travel internationally over the summer and could bring cases back into the country, the CDC alert warned. Symptoms include fever, chills and headaches.
Here at home, getting the insects to buzz off can be a tall order, especially for those with higher levels of certain acids on their skin that make them more attractive to some mosquitoes.
In a 2022 study published in the journal Cell, researchers from Rockefeller University in New York City found that people who produced higher levels of carboxylic acid were “mosquito magnets,” says scientist Maria Elena De Obaldia, who worked on the report. It’s unclear what causes people to have more (or less) of these acids on their skin.
“It’s possible that some people who are less attractive to mosquitoes than others express natural repellents,” De Obaldia says. “If this turned out to be true, we could use this information to try to design repellents that would make all of us smell more like the people who are less attractive to mosquitoes.”
Until then, we asked the experts to weigh in on what works — and what doesn’t — when it comes to mosquito prevention.
What works to repel mosquitoes
1. Bathing with coconut-scented soap
In contrast to fruity or floral-scented soaps that can lead to a mosquito feeding frenzy, coconut repels the biting insects, researchers at Virginia Tech found.
“We like to scent our soaps with chemicals typically associated with the pleasant scent of flowers and plants, but mosquitoes also use plant-emitted [scents] to find plants and obtain sugars from their nectar,” says researcher Clément Vinauger, an assistant professor in the biochemistry department at Virginia Tech, who was among a group that studied this issue.
Vinauger notes that coconut-scented products might even be more effective than mosquito repellents containing the active ingredient known as DEET. The takeaway: To discourage mosquitoes, lather up with coconut-scented soap and slather on coconut-scented sunscreen before heading outside.
2. Spraying the bottoms of walls
Did you know that by spraying just 12 percent of a room with insecticide you can kill 85 percent of mosquitos? A new study by researchers in Brazil found that significantly more mosquitoes (both male and female) frequently visited the bases of walls rather than the upper portions. That allows you to use less spray overall to kill more mosquitoes. Make sure to choose an insecticide that is generally safe for children and pets.
3. Wearing permethrin-treated clothing
Several brands and big box stores sell T-shirts, shorts, pants, socks, hats and other items that are treated with permethrin, a common synthetic insecticide designed to repel mosquitoes and other biting insects.
The U.S. Environmental Protection Agency first allowed clothing to be treated with permethrin in 1990, and studies show it works.
Permethrin-treated clothing was still effective after three months of wear, according to a study published in Parasites & Vectors, and a 2020 paper published in the Journal of Medical Entomology found that treated clothing is associated with 65 percent fewer tick bites. An earlier study from researchers in London found that wearing long-sleeved shirts and pants treated with the synthetic repellent reduced mosquito bites by 91 percent.
Katie Westby, a staff scientist in vector and disease ecology at Washington University in St. Louis, offers a word of caution.
Permethrin “should never be applied to skin; you treat your clothes with it,” she says. “It is harmful to pets, so it should be applied to clothing outdoors where animals will not come into contact with it.”
4. Switching up your wardrobe
Mosquitoes appear to use specific wavelengths on the visual spectrum to locate a target. Their preferred colors: red, orange, black and cyan (a greenish-blue), according to a study published by researchers at the University of Washington in the journal Nature Communications.
Opting for an outfit that is green, purple, blue or white — colors that mosquitoes avoid — could leave you with fewer bites during outdoor adventures.
Despite the potential for the color of your clothing to ward off mosquitoes, Westby says, “you would need to be completely covered for this to be an effective strategy to avoid bites.” But it can’t hurt to dress (not to) impress mosquitoes this summer.
5. Using insect repellent
Stick with the basics. Insect repellents that contain DEET are considered the gold standard when it comes to reducing bug bites and preventing mosquito-borne diseases.
The chemical signature in the insecticide interferes with the mosquito’s scent receptors, causing the insect to get confused and keep moving, and DEET-based products provide longer-lasting protection than insect repellents with other active ingredients.
Given the complex interaction of body odor, personal care products, diet and activity level that can make you more — or less — attractive to mosquitoes, Vinauger says, “I would still recommend using a conventional mosquito repellent.”
6. Lawn treatments
Pest companies offer treatments that blanket the lawn with insecticides to reduce mosquito populations. The treatments can work, though studies show that rainfall, the equipment used and application techniques can make them less effective — and the results might only be temporary.
Treatments “only kill mosquitoes that are in your yard at the time of spraying,” says Deborah Landau, director of ecological management for the Nature Conservancy. “Mosquitoes typically fly 1 to 3 miles, so they can quickly repopulate your yard.”
Lawn treatments can affect the ecosystem. Landau notes that the chemical sprays kill all insects, including bees, fireflies, butterfly larvae and other pollinators. “Birds often pick up insects killed by insecticides, and eat them or feed them to their young,” she adds.
When it comes to kids and pets, the research isn’t clear, according to Landau. It’s best to read manufacturers’ instructions, ask questions and proceed with caution.
3 things that don’t work
1. Citronella candles and plants
Citronella plants might look great in the garden, but they do little to deter biting bugs. Standing near the plants or having them in your garden doesn’t do much to keep mosquitoes at bay.
In fact, if you plant enough citronella, it could have the opposite effect.
“Finding natural alternatives to chemicals for repelling mosquitoes is an attractive option,” Westby says. “[But] there is evidence that having dense and flowering vegetation will attract mosquitoes to your yard, as they like to rest in cool, humid habitat and take sugar meals from flowers.”
You can skip the citronella-scented candles, too. Despite their reputation, research published in the Journal of Insect Science found that citronella candles had “no effect” on reducing the number of mosquitoes.
2. Spreading coffee grounds
It’s common for coffee companies to offer used grounds to gardeners, and the nitrogen-rich remnants from a morning cup of coffee can improve soil structure, suppress common fungal diseases and provide nutrients for earthworms. But there is no solid research showing that it prevents mosquito bites.
Older research found that coffee-treated water (in birdbaths, for example) might deter mosquitoes from laying eggs in those spots. You should always empty standing water in your yard to prevent mosquitoes from laying eggs there.
3. Using spatial repellents
Old-school mosquito coils and battery-operated devices that release insect repellents into the air are often used in enclosed or semi-enclosed spaces such as restaurant patios or screened porches. Although store shelves are stocked with spatial repellents of all kinds, their effectiveness is mixed. The latest research shows that mosquitoes took fewer full blood meals. The insects bit and moved on before getting full, which led them to bite more frequently and to spend more time in areas with spatial repellents — and no one wants to spend their summer with more mosquito bites.
Bug zappers don’t work well on mosquitoes or other biting flies, according to University of Delaware researchers. But beneficial bugs, including pollinators, are often killed by bug zappers.