DEET Insect Repellents

DEET bug repellent is the most effective overall

The synthetic pesticide DEET is registered by the Environmental Protection Agency (EPA) as safe to use on people of all ages. Even so, it's a chemical that makes a lot of people nervous, and the American Academy of Pediatrics (AAP)  recommends using a concentration of 30 percent or less on children and refraining from using DEET products altogether on infants younger than 2 months old.

An article published in AAP News says products with a concentration of 10 percent DEET are effective for approximately two hours, while a concentration of 24 percent may provide an additional three hours of protection. Expert reviews of products containing 30 percent DEET show it can provide protection for seven hours or longer. The duration of effectiveness varies from person to person and is likely to decrease when users perspire. DEET is approved as a repellent of mosquitoes and ticks, but some reviews say it's less effective on biting flies than products with other active ingredients.

Use of products containing DEET entails more precautions than bug repellers with other active ingredients. Because it is a solvent, DEET can damage synthetic materials it comes in contact with, such as fabrics, paint and plastics. To limit exposure to the chemical, care should be taken not to apply it to skin underneath clothing. After returning indoors, DEET repellents should be washed off the skin, and clothing sprayed with repellent should be removed. Experts estimate that many users don't follow these guidelines for proper use.

In addition to these inconveniences, some question the long-term health consequences of using DEET. Studies of DEET's effects on rats show that it's a neurotoxin, which in high concentrations damages brain cells and decreases mental and motor abilities, but these effects have not been proven in humans. DEET has been used and studied for about 60 years, more than any other insect repellent.

Reviews agree that bug repellers using DEET are consistently effective and that it's the percentage of DEET that makes one insect repellent protect for a longer time than another. Although mosquito repellents range in concentrations of DEET up to 100 percent, editors at ConsumerReports.org say "no one needs a repellent with more than 30 percent DEET." Once you've determined how long you need protection from biting insects, selecting a brand comes down to comparing the other ingredients, cost and physical attributes like scent and feel on the skin.

We found several aerosol products that fall well below the recommendation of 30 percent DEET or less, but deliver protection from mosquitoes and ticks for at least eight hours in tests. Off! FamilyCare Insect Repellent I Smooth & Dry (*Est. $6 for 4 oz.), for example, has only 15 percent DEET but is as effective as repellents with higher concentrations in one professional review. This product also scores well for odor and feel; testers describe the odor as "fruity" and say it dries quickly. It's only sold as an aerosol, but is also available in a smaller 2.5-oz. size.

Off! Deep Woods (*Est. $6 for 6 oz.) is an aerosol with 25 percent DEET that the manufacturer claims lasts for up to eight hours, but we didn't find any recent reviews to back up this claim. The New England Journal of Medicine tested Off! Deep Woods with 23.8 percent DEET in 2002 and says it is effective for only five hours. A study published in the 2004 Canada Communicable Disease Report finds it effective for only four to six hours, but the concentration of DEET isn't specified. Off! Deep Woods also comes in pump sprays and wipes in several sizes. Cutter Backwoods Unscented Insect Repellent (*Est. $9.50 for 6 oz.) with 23 percent DEET is another option in a pump spray or aerosol. In one laboratory test, it successfully repelled mosquitoes and ticks for at least eight hours. Testers say it has little odor and feels light on the skin. The manufacturers of all these DEET products say they protect against mosquitoes, ticks, biting flies, gnats, chiggers and fleas.

For a brief exposure of an hour or two, a low concentration of 5 percent to 10 percent DEET should do the trick. According to one professional review, Cutter Skinsations Insect Repellent (*Est. $8 for 6 oz.) with 7 percent DEET protects 4 to 6 hours against mosquitoes and seven hours against ticks. However, a 2002 review at Good Housekeeping magazine found it to be effective for roughly one hour on five test subjects who placed their arms in cages with 80 mosquitoes. We aren't sure what causes this discrepancy in findings. Cutter Skinsations is only available as a pump spray. Because it contains a low percent of DEET, it's not particularly greasy, and some may like that aloe and vitamin E are added as moisturizers. Off! FamilyCare Insect Repellent IV Unscented (*Est. $6 for 6 oz.) is another 7 percent DEET product, which The New England Journal of Medicine says lasts about two hours.

Slow-release formulas limit exposure to DEET

Reviews note that you can minimize DEET absorption by using a controlled-release DEET bug repellent. These products encapsulate DEET in a polymer so it doesn't penetrate the skin as much. Instead, the DEET stays on the skin's surface where it works to repel insects. Another plus: Slow-release products don't use alcohol. Alcohol opens the pores of the skin and creates more exposure to the DEET, and people with sensitive skin may experience an adverse reaction to the alcohol. While reviews testing controlled-release bug repellents find that they don't necessarily extend the protection time against bites, experts do confirm that these products serve to minimize your exposure to DEET.

3M Ultrathon was the first controlled-release product to emerge on the insect repellent market and is primarily sold at specialty retailers of outdoor gear. It was developed for the U.S. military and is still used by troops today. The manufacturer claims 3M Ultrathon Insect Repellent 12 Lotion (*Est. $9 for 2 oz.), which contains 34 percent DEET, lasts for up to 12 hours and repels mosquitoes, ticks, biting flies, chiggers, gnats and fleas.

The Canada Communicable Disease Report found this lotion to be effective for 8 to 12 hours, but two other expert reviews reveal shorter periods of effectiveness. Editors at Which? magazine in the U.K. found it to last seven hours, which is still longer than any of the other 18 insect repellents tested. It also outperformed 15 other insect repellents (including Repel Lemon Eucalyptus Insect Repellent) tested by Backpacker magazine with an effectiveness of six hours. One shortcoming of the latter study is the use of a single test subject.

3M Ultrathon Insect Repellent 8 Spray (*Est. $7.50 for 6 oz.) with 25 percent DEET repels both mosquitoes and ticks for at least eight hours in another professional review. Testers describe the odor as strong and say this aerosol feels greasy. The similar 3M Ultrathon Insect Repellent Pump contains 19 percent DEET (*Est. $9 for 6 oz.) and should last for up to three hours.

If you don't need 12 hours of protection, Sawyer Controlled Release Insect Repellent (*Est. $10.50 for 6 oz.) has 20 percent encapsulated DEET. According to a comprehensive study by The New England Journal of Medicine using 15 volunteers, Sawyer Controlled Release lasts an average of four hours; however, the Canada Communicable Disease Report says it is effective for at least eight hours. Sawyer claims this product reduces absorption of DEET by 67 percent and is odorless. The few user reviews at Amazon.com and REI.com are positive.

Picaridin and IR3535 are alternatives to DEET

Picaridin, another synthetic chemical, is often used as a repellent against mosquitoes, ticks and biting flies. Insect repellents containing picaridin have been available in the U.S. since 2005, but
a higher concentration of 20 percent wasn't available until 2008. Effectiveness increases with higher concentrations of picaridin -- 20 percent lasts roughly two hours. Like DEET, this chemical is registered with the EPA as safe for people of all ages. Even though mosquito repellent with picaridin doesn't last as long as DEET, some people prefer it because the compound is odorless, doesn't need to be washed off your skin (it feels lighter), and doesn't damage synthetic materials. Generally, we found fewer expert reviews for this type of bug repeller, most likely due to the limited number of products available that contain it.

In one test, Natrapel 8-Hour Insect Repellent (*Est. $6 for 3.5 oz.), with 20 percent picaridin, performed nearly as well as products containing DEET. Although it repelled Culex mosquitoes and ticks for at least eight hours, Aedes mosquitoes started biting test subjects after seven hours. A handful of users at Drugstore.com give it a high overall rating of 4.5 stars out of 5. They say it works as well as DEET products and smells better. In addition to a pump spray, Natrapel is also available in a 5-oz. continuous spray or wipes.

Cutter Advanced Insect Repellent (*Est. $5.50 for 6 oz.), a pump spray with 7 percent picaridin, is the top pick at About.com, primarily because it's odorless. It is also included in a rather informal test by Andria Lisle, a writer at Slate.com, but was found to be ineffective against gnats and "mosquitoes flocked back after a mere 90 minutes." It can be applied up to three times a day, but that still falls well short for an all-day excursion outdoors. Testers confirm it's odorless and doesn't feel sticky. Amazon.com and Drugstore.com have each accumulated about a dozen user reviews for this bug repeller, where it gets an overall rating of about least 4 stars out of 5. Most users find it effective, but wish it was longer lasting. They also prefer the smell and non-greasy feel of it to DEET products.

We found no expert reviews of Off! FamilyCare Insect Repellent II Clean Feel (*Est. $5 for 6 oz.), which contains just 5 percent picaridin. A handful of reviews at Drugstore.com and Amazon.com are mixed about its effectiveness. The consensus, however, are happy with how it feels and smells. It is only sold as a pump spray.

Another synthetic ingredient called IR3535 is reasonably effective as a bug repellent, but it's easier to find in Europe. In the United States, Avon combines it with sunscreen in the product Avon Skin So Soft Bug Guard Plus IR3535 (*Est. $14 for 4 oz.), which is available in pump spray or lotion. However, the CDC doesn't recommend using a product containing both mosquito repellent and sunscreen (because sunscreen needs to be reapplied more frequently than repellent). Plus, a University of Florida study recently found that the repellent in combination products tends to get absorbed into the skin more than in repellent-only products.

In one professional review, Avon's product more readily damaged materials than repellents containing DEET and picaridin. However, at Backpacker magazine, it lasted three hours on a single test subject, which was longer than many of the other 14 products tested. About 30 user reviews at the Avon website give it a high average rating of 4.7 stars out of 5. Users say it works well at repelling mosquitoes and black flies, and it has a pleasant smell. About 10 user reviews at Amazon.com are happy with its effectiveness, but one says she damaged a plastic object she touched after applying it.