Sprays, ultrasonic devices, wristbands, citronella candles: There’s a ton of products on the market that promise to keep away mosquitoes, ticks, and other bothersome bugs. But which products best protect against these biting and bloodsucking pests?
It’s important to protect yourself, as mosquitoes and ticks can transmit debilitating diseases like West Nile virus and Lyme disease. Yet not all repellents are created equal, and some don’t work at all. The repellent you might want to use depends on where you live, how long you’ll be outdoors, and which bugs you’re trying to repel. It also comes down to personal preferences, like fragrance strength.
Mosquitoes are attracted to the “bouquet” of scents on your skin, according to Conor McMeniman, an entomologist and infectious disease expert at Johns Hopkins University.
These are chemicals our bodies produce as they break down sugars and proteins for energy, like lactic acid and carbon dioxide, as well as those produced by bacteria on the skin. Some people smell more tantalizing to mosquitoes based on their unique cocktail of chemicals. Scientists believe that repellents disrupt mosquitoes’ and ticks’ ability to smell us.
Here’s what works
The EPA keeps a handy list of compounds that effectively fight off disease-harboring pests, and tells you which pests each repellent keeps away. These repellents have a relatively low environmental toxicity and are safe for humans in accepted doses.
Of these, DEET was the first chemical-based repellent on the market, and some experts consider it to be the most effective against many biting insects, says Dan Markowski, technical advisor at the American Mosquito Control Association.
Although repellents are sold in concentrations of up to 100 percent DEET, protection doesn’t get better after about 50 percent, says Erika Machtinger, an entomologist and chemical ecologist at Pennsylvania State University, and even low concentrations offer good protection. There is a negligible increase in how well a repellent works once its DEET concentration gets above 30 percent; the EPA recommends between 10-30 percent.
The EPA also states that DEET most likely doesn’t pose a risk to the environment, at least the way we use it on ourselves. According to the National Pesticide Information Center, while DEET stays in the soil and wastewater, it degrades quickly. Several studies have shown the concentrations of DEET found in streams and rivers are too low to do damage to aquatic wildlife. The same goes for all other products on the EPA’s list, explains Machtinger: all of them have been scientifically tested for safety for humans and wildlife.
DEET can, however, ruin your favorite pair of shorts. DEET degrades spandex and other plastics, meaning you might want to be careful with what you wear if you also spray yourself with DEET products. And as Machtinger points out, “it smells horrible and it’s greasy.” She opts for products that contain picaridin herself, but notes that it’s harder to find than DEET.
Adelaide Herbert, a dermatologist at UTHealth Houston, says DEET is considered safe for most adults, but ingesting large amounts has been linked to seizures. She adds that pregnant women and young children may want to find an alternative to DEET (she usually recommends picaridin to protect against mosquitoes).
Many experts consider picaridin to work just as well as DEET, and it may even last a bit longer. They both offer protection against a slew of irritating insects, including biting flies, gnats, ticks, chiggers, and fleas.
Outdoorsy types may want to consider using permethrin on their clothes. It’s another EPA-approved repellent that not only masks human scent but also acts as an insecticide, killing insects on contact, says Herbert.
Permethrin is super effective, especially against ticks, says Herbert, and the EPA hasn’t found any evidence that permethrin-treated clothing is toxic to humans or wildlife when used as directed. When applying, avoid getting it on your skin as it can cause irritation. It’s toxic to humans when swallowed, especially for young children. As a pesticide, permethrin is extremely harmful to aquatic organisms and beneficial insects—so you should also be mindful where you spray it and only use it following directions on the label.
Other options may not work as well
Other chemicals may be EPA-certified but less effective. Experts add that products that aren’t sprayed on your person don’t offer much protection.
IR3535 is also a good option if you want something completely odorless. It offers strong protection against mosquitos and other insects, but doesn’t last as long as DEET and picaridin, and it’s a bit harder to find in the U.S.
For those that want a completely plant-based option, oil of lemon eucalyptus is the only plant-derived repellent that most experts recommend. Its active ingredient, PMD, is effective against mosquitoes and ticks (although less so than other options), but not chiggers and other biting insects. It also can’t be used in children under three years old, as it can cause skin irritation.
Be wary of other essential oils—”every bottle you buy” can have different contents, are often not tested for safety, can cause skin reactions, and even kill beneficial insects, says Machtinger.
Opting for a bracelet, clip-on, or sticker is probably ill-advised, says Markowski, even if the wearable product contains an EPA-approved chemical. “I get it, no one likes to put DEET on. But these just don’t really work, ” Markowski says. “The reason is that when there’s a strong gust of wind, or even when you walk too fast, the cloud of repellent around the product doesn’t follow, leaving you unprotected.”
One thing most experts agree on is that citronella candles aren’t effective. Studies showed citronella candles and incense only decreased the chance of a bite by about 20 to 40 percent (DEET decreases these chances by more than 95 percent). Wind can also disperse or douse the candle’s flame, meaning mosquitos will come find you anyway, Markowski explains.
There are some products that heat up and release synthetic pyrethroids, which work in calm weather. But the elements can also render these products useless. These pyrethroids are also harmful to aquatic species, so you shouldn’t use them if you live near a stream or lake.
Multiple experts also agreed that zappers and ultrasonic devices are completely ineffective.
The bottom line, says Machtinger, is that you should read the label, do your research about bugs in the area, and make sure to reapply if applicable.
“The best thing you can do is just be prepared and remember to protect yourself,” Machtinger says. “An ounce of prevention goes a long way.”