How Bad Is It Really to Use DEET?

Whether you're outside hiking, gardening or grilling, slathering on insect repellent is a must. Not only can it prevent itchy, annoying bites, but more importantly, it defends against serious illness, such as Lyme disease or West Nile virus.

According to the Centers for Disease Control and Prevention (CDC), the number of disease cases from infected mosquitos, ticks and fleas has tripled in the U.S. over the past 13 years.

"Tickborne diseases are spreading as deer ticks expand their range and colonize new areas in the northern part of the U.S.," says Jonathan Oliver, PhD, assistant professor at the University of Minnesota School of Public Health. "In addition, new diseases like chikungunya and zika [which are transmitted by mosquitos in subtropical areas] have come about."

The dangers are no joke, yet some folks are hesitant to reach for that bottle of OFF! They're wary that the ingredients used to ward off critters — namely DEET — might also be harmful for their personal health. A 2018 Consumer Reports survey found that 25 percent of people avoid products containing DEET and one-third believe that DEET-containing repellents are not as safe as other options.

So we reached out to experts specializing in insecticides and public health to find out the safest way to armor up and keep away bugs.

Meet DEET: "DEET is an active ingredient that is used to repel biting insects," says Carla Burns, senior director of cosmetic science at the Environmental Working Group (EWG). Its scientific name is ​N,N​-diethyl-​m​-toluamide, and a June 2016 study in ​Nature​ suggests that it's the most effective and widely used insect repellent in the world.

"It has been around and used heavily for decades," Oliver says.

According to the Environmental Protection Agency (EPA), DEET was developed by the U.S. Army in the 1940s for military use and became available to the public in 1957. It quickly gained popularity because it works incredibly well.

It doesn't actually kill creepy-crawlies. "Rather, DEET application on skin deters insect bites," Burns says.

To understand the way it operates, let's look at how pests locate their human hosts. "Ticks and mosquitos are attracted to chemicals people produce, primarily carbon dioxide," Oliver says. "They detect carbon dioxide in the air and follow this plume until they reach you."

Spritzing on DEET is kind of like wrapping yourself in an invisibility cloak that makes it more difficult for bugs to find you. "We don't understand all the details of how it works, but it disrupts insects' sensory system so that they don't notice people as well," Oliver says.

Cue the sigh of relief: Despite the large chunk of the population that believes DEET is hazardous to your health, it's actually super safe. "It is one of the best-studied chemicals, and none of the research has found serious issues from long-term exposure," Oliver says. "The science is in agreement that it is more or less harmless for application on unbroken skin."

A June 2014 study in ​Parasites & Vectors​ determined there was no evidence of severe negative side effects. And the CDC asserts that, as long as you use it as directed — meaning: don't swallow it, inhale it or aim the nozzle at your eyes — the worst that can happen is skin or eye irritation. In rare cases, DEET has been associated with rashes.

As for concerns that it causes cancer? Debunked! "DEET is not classified as a human carcinogen and I am not aware of any studies that show a link between cancer and DEET exposure," Burns says.

So if DEET is NBD, why are some people convinced it's dangerous? "One component could be that it has a strong chemical odor," Oliver says. Plus, some of us might conflate DEET with DDT — a potent insecticide that was banned in 1972 due to environmental toxicity and human health risks.

Here's how to get the most out of your insect repellent.

"Familiarize yourself with the risks in your area," Oliver says. "For instance, in some places ticks are not a concern; in others they are the main worry."

Then, scan the label of your repellent to make sure it defends against the pests in your 'hood.

Bug sprays can only be registered with the EPA if they have been tested and proven to be safe and effective for humans, including children and pregnant women. (The EWG cautions against using any bug spray on infants under 6 months old.) Check the bottle for an EPA registration number or select a product from this list.

Confirm how much DEET your bug spray contains. According to the CDC, the concentration ranges from 4 to 100 percent.

"There is no difference in effectiveness if a product has a higher DEET concentration, but it will last longer," Oliver says. For example, a repellent with 7 percent DEET will protect you for about two hours, while 98 percent DEET shields you for up to 10 hours.

Because it's always a good idea to reduce your overall chemical exposure and minimize the chance of skin reactions, opt for the lowest DEET concentration needed for the length of time you'll be in a buggy area. (Or, you can reapply a low-concentration product as instructed to extend your protection.)

"We urge consumers to choose products that limit DEET to 30 percent and avoid higher concentrations," Burns says.

At the end of the day, wash off bug spray with soap and water.

Read the label to see how frequently you should reapply. Per the CDC, spray on more if you go swimming, get very sweaty or are being eaten alive (some people attract more bugs than others).

"Be sure to hit your ankles and shoes," Oliver says. "Mosquitos are strongly attracted to the skin biota that makes your feet smell, and DEET will mask that odor."

Plus, ticks primarily hang out on the ground.

Spritz a thin film of repellent onto exposed skin and clothing — there is no need to put it directly on skin that's covered in clothes.

To avoid contact with your eyes and mouth, the EPA suggests spraying repellent into your palms and then smoothing it over your face. (Remember to wash your hands after.) Don't put it on broken or irritated skin, and never mist it on in an enclosed space or near food.

When putting DEET on kids, spray it into your hands first and then wipe it on their skin or clothes, steering clear of their hands, mouth, nostrils and eyes.

"Aerosol sprays carry inhalation concerns and a greater risk for eye irritation," Burns says.

"They are less effective than applying a repellent to your skin or clothing," Burns says. "They also have a limited radius of protection."

Here's the 101 on other ingredients that can protect against skeeters and ticks.

​1. Picaridin:​ This repellent hit the market in 2005 and isn't associated with any worrisome health concerns. The EWG points out that it won't aggravate your skin, smells better than DEET and may last longer.

​2. IR3535:​ The EWG reports that the only safety concern with IR3535 is eye irritation. It is slightly less effective than DEET and picaridin in warding off mosquitos, but offers more than double the protection time against deer ticks.

​3. Oil of Lemon Eucalyptus:​ If you want a botanical option that actually does the trick, this is it. An extract from the eucalyptus tree in Australia, oil of lemon eucalyptus (and its synthetic derivative, PMD) has been shown in some tests to work as well as DEET, although the effects only last a couple of hours. "It also has a pleasant odor," Oliver says.

On the downside, research into oil of lemon eucalyptus is limited, and as a result, it's not recommended for children under age 3. "In contrast, DEET has been very well studied for over 60 years and we have a good idea of its safety profile," Oliver says.

With the exception of oil of lemon eucalyptus, it's probably best to pass on products containing plant extracts. "Due to lack of testing, we don't know how safe or effective they are," Oliver says. Plant-based repellents often keep away insects for only a short period of time, if at all.

"And be aware that many botanical products contain highly concentrated allergens and may irritate your skin," Burns says.

​4. Permethrin:​ If you spend a lot of time in tick-infested woods, permethrin might be a good choice. You can either buy clothing treated with permethrin or spray it directly onto gear, like boots and tents. "It is very effective because ticks and mosquitos die when they come into contact with it," Oliver says. "But don't ever touch it while wet, as it is quite strong."

Although the EPA maintains that permethrin-permeated clothing is safe, it is highly toxic to the environment and a likely human carcinogen. It can also dissipate over time and after a certain number of washings.

Don't bug out! It's OK to spray away.

"DEET's toxicity profile is better than many people assume, and the rate of adverse reactions is low," Burns says. "Weighed against the consequences of a life-changing disease [from an infected mosquito or tick], an insect repellent that uses no more than 30 percent DEET is a reasonable choice."