Whether you live in a warm-weather climate, are planning a tropical vacation, or are just stocking up early for the summer, choosing spray-on insect repellent over “wearable” devices will give you the best protection against mosquitos, says a new study. The research tested the effectiveness of 10 commercial products against Aedes aegypti, the species of mosquito that carries Zika and other viruses.
Sprays that contain DEET and PMD (the chemical name for the oil of lemon eucalyptus) took top honors, say researchers from New Mexico State University. That was no big surprise, since these ingredients are registered with the Environmental Protection Agency and recognized by the Centers for Disease Control as effective at preventing mosquito bites.
Other products—including mosquito bracelets, a wearable sonic repeller, and a citronella candle—were significantly less effective.
For the study, published this week in the Journal of Insect Science, human volunteers wore or used the products, one at a time, in an enclosed space near a cage containing female Aedes aegypti mosquitoes. After 15 minutes, researchers noted the mosquitoes’ locations—either close to or far away from the human subject—to see how attracted they were (or weren’t) to the person.
The five spray-on repellents that were tested all provided some protection, although Cutter Lemon Eucalyptus (30 percent PMD) and Ben's Tick & Insect Repellent (98 percent DEET) were the most effective. Following the two winners, in order of effectiveness, were All Terrain Kids Herbal Armor (a blend of natural oils), Avon Skin-So-Soft Bug Guard Plus Picaridin (which contains the active ingredient picaridin), and Repel Sportsmen Max Formula (40 percent DEET).
Three bracelets containing geraniol oil—Mosquitavert, Mosquito-NO!, and Invisaband—showed no significant protection against mosquito attraction. Neither did the PIC Personal Sonic Mosquito Repeller, which claims to use inaudible sound waves to repel bugs, or the Cutter Citro Guard, a candle containing citronella oil.
“These products advertise that they protect you for several hours or longer, but they definitely fell short,” says Stacy Rodriguez, laboratory manager at the Molecular Vector Physiology Laboratory at NMSU. (One bracelet advertised protection for up to 10 days!) “It’s something that consumers really need to be aware of, that not all wearable devices are trustworthy.”
Citronella hasn’t proven to provide much protection against mosquitoes, says co-author Immo Hansen, PhD, associate professor of molecular vector biology. “And even if bracelets contain other ingredients, they don’t seem to have the dosage to be effective,” he says.
The only wearable that fared well in the test—better than the sprays, actually—was the OFF! Clip-on, a small disk that weighs about six ounces and contains a tiny fan and nebulizer. The device vaporizes and disperses the chemical metofluthrin, and is marketed as providing head-to-toe protection for up to 12 hours.
Avoiding pesky mosquito bites is always a good thing. But at a time when mosquito-borne diseases like Zika, chikungunya, and dengue fever are a serious threat, says Rodriguez, it’s especially important for consumers to use a product that really works.
Make sure you apply bug spray as directed, as well. “A lot of people spray themselves once and think they’re protected for hours,” says Rodriguez. Depending on the product you’re using, she says, that may be true. But some sprays need more frequent application—and activities involving water or sweat can make even the strongest formulas wear off faster.