People will go to some ridiculous lengths to avoid mosquito bites. They burn cow dung, coconut shells, or coffee. They drink gin and tonics. They eat bananas. They spray themselves with mouthwash or slather themselves in a clove/alcohol solution. They also dry themselves with Bounce. “You know, those nice-smelling sheets you put in the dryer,” said Immo Hansen, PhD, a professor at the Institute of Applied Biosciences at New Mexico State University.
None of these methods have been tested to see if they actually repel mosquitoes. But that hasn’t stopped people from trying them, according to a study to be published this summer by Hansen and his colleague Stacy Rodriguez, who runs Hansen’s lab at New Mexico State University. Stacy Rodriguez studies ways to prevent mosquito-borne diseases. She and her colleagues surveyed 5,000 people about how they protect themselves from mosquito bites. Most people used traditional mosquito repellents.
The researchers then asked them about traditional home remedies. That’s where cow dung and dryer paper come in. In an interview, Hansen and Rodriguez shared some of the answers they received. Their paper was published in the peer-reviewed journal PeerJ.
Beyond folk remedies and traditional defenses, there are other proven ways to protect yourself from mosquitoes and the diseases they carry. NPR spoke with researchers, many of whom spend a lot of time in mosquito-infested jungles, swamps, and tropical areas.
Products containing DEET have been shown to be safe and effective. DEET is an abbreviation for the chemical N,N-diethyl-meta-toluamide, which is the active ingredient in many insect repellents. A 2015 paper published in the Journal of Insect Science looked at the effectiveness of various commercial insecticides and found that products containing DEET were effective and relatively long-lasting. Rodriguez and Hansen were the authors of the 2015 study, which they replicated in a 2017 paper in the same journal.
DEET hit store shelves in 1957. There were initial concerns about its safety, with some suggesting it could cause neurological problems. However, more recent reviews, such as a June 2014 study published in the journal Parasites and Vectors, note that “animal tests, observational studies, and intervention trials have found no evidence of serious adverse effects associated with the recommended use of DEET.”
DEET isn’t the only weapon. Products containing the active ingredients picaridin and IR 3535 are equally effective, says Dr. Dan Strickman of the Bill & Melinda Gates Foundation’s Global Health Program (an NPR sponsor) and author of Preventing Insect Bites, Stings, and Disease.
The Centers for Disease Control and Prevention reports that repellents containing any of these active ingredients are safe and effective. These repellents are widely used around the world.
“Picaridin is more effective than DEET and appears to repel mosquitoes,” he said. When people use DEET, mosquitoes may land on them but won’t bite. When they use products containing picaridin, mosquitoes were even less likely to land. Repellents containing IR 3535 are slightly less effective, Strickman said, but they don’t have the strong odor of other products.
There’s also petrolatum lemon eucalyptus (PMD), a natural oil derived from the lemon-scented leaves and twigs of the eucalyptus tree, which is also recommended by the CDC. PMD is the component of the oil that repels insects. Researchers at New Mexico State University found that products containing lemon eucalyptus oil were just as effective as those containing DEET, and the effects lasted longer. “Some people have a stigma about using chemicals on their skin. They prefer more natural products,” Rodriguez says.
In 2015, a surprising discovery was made: Victoria’s Secret’s Bombshell scent was actually quite effective at repelling mosquitoes. Hansen and Rodriguez said they added it to their test products as a positive control because they thought its floral scent would attract mosquitoes. It turns out mosquitoes hate the smell.
Their latest study, from 2017, also yielded surprises. The product, called Off Clip-On, attaches to clothing and contains the regional insect repellent metofluthrin, which is also recommended by the CDC. The wearable device is designed for people who sit in one place, such as parents watching a softball game. The mask wearer turns on a small battery-powered fan that blows a small cloud of repellent mist into the air around the wearer. “It actually works,” Hansen said, adding that it’s as effective at repelling insects as DEET or oil of lemon eucalyptus.
Not all products deliver the results they promise. A 2015 study found that vitamin B1 patches were ineffective at repelling mosquitoes. A 2017 study included citronella candles among the products that did not repel mosquitoes.
Recent studies have shown that so-called mosquito repellant bracelets and bands do not repel mosquitoes. These products contain various oils, including citronella and lemongrass.
“I’ve had mosquito bites on the bracelets I’ve tested,” Rodriguez said. “They advertise these bracelets and bandages as protection against Zika [a mosquito-borne virus that can cause serious birth defects in pregnant women], but these bracelets are completely ineffective.”
Ultrasonic devices, which emit tones that humans can’t hear but that marketers claim mosquitoes hate, also don’t work. “The sonic devices we tested had no effect,” Hansen said. “We’ve tested other devices before. They were ineffective. There’s no scientific evidence that mosquitoes are repelled by sound.
Experts say it’s generally smarter to follow manufacturer instructions. If people are going to be outdoors for an hour or two, they should use products containing lower concentrations of DEET (the label says about 10 percent) for protection. Dr. Jorge Rey, acting director of the Florida Medical Entomology Laboratory in Vero Beach, said that if people are going to be in wooded areas, jungles, or swamps, they should use a higher concentration of DEET — 20 percent to 25 percent — and change it about every four hours. “The higher the concentration, the longer it lasts,” Rey said.
Again, follow the manufacturer’s dosing instructions. “A lot of people think that if it’s good in small amounts, it’s even better in large amounts,” said Dr. William Reisen, professor emeritus at the University of California, Davis School of Veterinary Medicine. “You don’t have to bathe in the stuff.”
When Ray goes into pest-infested areas, like Florida’s Everglades National Park, to conduct research, he wears protective gear. “We’ll wear long pants and long-sleeved shirts,” he said. “If it’s really bad, we’ll put hats with nets over our faces. We rely on exposed parts of our bodies to repel mosquitoes.” That could mean our hands, neck, and face. However, experts advise against spraying it on your face. To avoid eye irritation, apply the repellent to your hands, then rub it on your face.
Don’t forget about your feet. Mosquitoes have unique olfactory preferences. Many mosquitoes, especially the Aedes mosquitoes that carry the Zika virus, like the smell of feet.
“Wearing sandals is not a good idea,” Rodriguez said. Shoes and socks are essential, and tucking pants into socks or shoes will help prevent mosquitoes from getting into your clothes. In mosquito-infested areas, she wears long pants and definitely not yoga pants. “Spandex is mosquito-friendly. They bite through it. I wear baggy pants and long-sleeved shirts and put DEET on.”
Mosquitoes can bite at any time of day, but the Aedes aegypti mosquito that carries the Zika virus prefers the morning and evening hours, Strickman said. If possible, stay indoors with window screens or air conditioning during these times.
Because these mosquitoes breed in standing water in containers such as flower pots, old tires, buckets and trash cans, people should remove any areas of standing water around them. “Swimming pools are acceptable as long as they are not abandoned,” Ray said. Chemicals used to make pools safe can also repel mosquitoes. Close surveillance is required to find all possible mosquito breeding sites. “I’ve seen mosquitoes breeding in the film of water near sinks or in the bottom of the glass people use to brush their teeth,” Strickman said. Cleaning up areas of standing water can significantly reduce mosquito populations.
The more people who do this basic cleaning, the fewer mosquitoes there will be. “It may not be perfect, but the mosquito population will be significantly reduced,” Strickman said.
Hansen said his lab is working on a technology to sterilize male mosquitoes with radiation and then release them into the environment. The male mosquito mates with a female, and the female lays eggs, but the eggs do not hatch. The technology would target specific species, such as the Aedes aegypti mosquito, which spreads Zika, dengue fever and other diseases.
A team of Massachusetts scientists is working on a mosquito repellent that will stay on the skin and last for hours or even days, said Dr. Abrar Karan, a physician at Brigham and Women’s Hospital. He is one of the inventors of Hour72+, a repellent that he says does not penetrate the skin or enter the bloodstream, but is rendered ineffective only by the skin’s natural shedding.
This year, Hour72+ won the $75,000 Dubilier grand prize at Harvard Business School’s annual startup competition. Karan plans to conduct further testing of the prototype, which is not yet commercially available, to see how long it can operate effectively.
Post time: Mar-17-2025