Effective Repellants To Ward Off Mosquitoes
In test of eleven products, a fogger and DEET worked, herbs and citronella didn’t.
Already daydreaming about warm, outdoor barbecues and picnics? If so, one thing you’re probably leaving out of your happy vision is the inevitable return of blood-thirsty mosquitoes that crash those otherwise relaxing outdoor events.
Luckily, this year, researchers have your back, as Science first reported.
In a high-tech experiment to recreate your bite risks while chilling on your patio, researchers at New Mexico State University tested out 11 common types of mosquito repellent to find the most effective ones.
The results: stick with DEET-containing products, metofluthrin-blowing clip-on fans, and sprays containing oil of lemon eucalyptus. The results appear in the Journal of Insect Science.
To test out the products, the researchers set up a three-chamber cage of mosquitoes in a wind tunnel, gently blowing at 2 meters/second.
Here's how the experiment works: A pack of hungry Ae. aegypti mosquitoes (50 to 125) enters into the middle compartment and can fly to either side—upwind or down.
Next, the researchers place some delicious human “bait” one meter upwind of the cage. (The researchers made sure that volunteers didn’t bathe in the 15 hours prior so that the mosquitoes could get a good whiff.)
After a little time, the researchers seal off the chambers and tally up how the mosquitoes distribute—toward the bait or not.
In a positive control, 88.8 percent stalked the chamber closest to the bait. In a negative control with no bait, only 17 percent roamed the upwind chamber.
Next, the researchers tried out 11 different types of mosquito repellant on the bait. The products included bracelets, wearable devices, sprays, and citronella candles. The most effective products were, in order of rank:
- The OFF! Clip-on, which is a wearable device that spews a fog of metofluthrin insecticide. Only 27 percent of mosquitoes were in the upwind chamber, about a 70 percent reduction in mosquito attraction.
- Cutter Lemon Eucalyptus, a spray of oil of lemon eucalyptus. Only 29.6 percent of the mosquitoes were in the upwind chamber.
- Ben’s Tick & Insect Repellent, a spray-on containing 98 percent DEET. Only 33.7 percent of mosquitoes were in the upwind chamber, a reduction of around 60 percent.
The personal sonic mosquito repellent, citronella candle, herbal sprays, and bracelets did virtually nothing.
The authors are hopeful that the information can better inform consumers about how to best protect against bites. “At a time where vector-borne diseases like Zika are a real threat, the most egregious danger to the consumer is the false comfort that some repellents give them protection against Ae. aegypti when they actually offer none,” the authors conclude.
Beth is Ars Technica’s health reporter. She’s interested in biomedical research, infectious disease, health policy and law, and has a Ph.D. in microbiology.