Citronella Candles Don't Repel Mosquitoes

Summer is when you enjoy the outdoors, which means mosquitoes are enjoying eating you alive. It's no wonder, then, that summer is also full of myths about how to keep those little bugs at bay. Myth number one? Light a citronella candle. A 2017 study showed that citronella — along with a whole bunch of other substances — does nothing to deter mosquitoes. Luckily, there are a few that really do.

Mosquito Misses

For a 2017 study published in the Journal of Insect Science, researchers recruited two volunteers who had previously been proven to be highly attractive to mosquitoes and were asked to not bathe or use personal hygiene products for the day leading up to the experiment. (Ah, the things we do for science.) The "human bait," as the study called the volunteers, sat at one end of a low-intensity wind tunnel and waited for mosquitoes to move toward them from a cage at the other end, where scientists counted the insects. In each test, the volunteers wore one of 11 different products, which ranged from standard insecticides to natural oils to sonic repellers.

The results were ... not good. The citronella candle actually attracted more mosquitoes than the volunteer by himself. Among the three mosquito-repellent bracelets they tested, none were effective. That was true even when the bracelet contained a chemical known to repel mosquitoes, which led the researchers to theorize that the concentrations in bracelets are too low to have any effect. And sonic repellers? Well, previous research has already debunked their usefulness, and this study was no different. "We are not aware of any scientific study showing that mosquitoes can be repelled by sound waves and therefore we consider these devices as the modern equivalent of snake oil," the authors quipped.

What Does Work?

It's not all bad news. Several products had real effects. A few shouldn't be surprising: the standard insecticide known as DEET successfully repelled the bitey little bugs, as did a wearable fogger that emitted the chemical metofluthrin. If you're looking for a natural solution, oil of lemon eucalyptus spray (known chemically as PMD) at 30 percent concentration was just as effective as DEET. That lines up with previous research and is handy information for anyone looking to avoid using synthetic insecticides.

Now, go forth and enjoy your picnics. And tell the mosquitoes Curiosity sent you.

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You can buy the exact concentration of oil of lemon eucalyptus spray that the study found to be so effective right here. That's an affiliate link. If you use it to make a purchase, Curiosity will get a share of the sale.

Written by Ashley Hamer July 19, 2017

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