EXPLORE TOPICS
Visit the companion blog
This Green Life
A monthly journal of sorts by Sheryl Eisenberg

JUNE 2010 (links updated 2012): DEET keeps the bugs away, including mosquitoes and ticks that carry serious diseases. But it also carries risks of its own. Should you use it?

Bug Spray, Examined
DEET vs. the alternatives

DEET is not the only insect repellent that works, but may be the most effective against the widest range of bugs. It is also a synthetic chemical with known and suspected adverse effects on human health.

That makes for a quandary. Should you use products made with DEET or try a newer—or natural—alternative: in particular, Picaridin, lemon eucalyptus oil or soy oil? There is no one-size-fits-all answer, but following are the things to consider when making your choice.

THE FACTS ABOUT DEET

Toxicity: According to the Environmental Protection Agency (EPA), the "acute toxicity" of DEET is low, meaning adverse effects are mild and temporary—mainly rashes. A few cases of seizures have been reported, but the link to DEET is inconclusive, says the EPA.

So far so good. However, the EPA's safety review was conducted in the 1990s, and the research it was based on did not adequately explore chronic toxicity. More recent research shows that DEET is a neurotoxin and could have long-term effects. Moreover, DEET may increase the toxicity of other chemicals to which people are exposed. For instance, people wearing DEET more easily absorb 2,4-D, a toxic weed killer that was used in Agent Orange and is now commonly used on lawns.

Clearly, more research is needed into the long-term health effects of DEET—especially on children. (One third of children in the U.S. are estimated to use DEET-based products.)

Also note that there are additional risks from very high doses of DEET and prolonged exposure. The National Institutes of Health says the high levels to which military personnel or game wardens might be exposed could lead to severe skin reactions (blisters, burning and scars), insomnia and mood changes. Completely improper use, such as swallowing, has its own, serious hazards.

Concentration: In the U.S., you can buy products with up to 100% DEET, but NRDC senior scientist Gina Solomon recommends 30% or less. While protection time increases with higher concentrations, it plateaus by 50%, and the protection afforded by 30% is sufficient for almost all circumstances. In Canada, 30% is the legal limit.

Safe usage: The EPA believes that "the normal use of DEET does not present a health concern to the general U.S. population." But "normal use" does not really mean normal use. It means careful use of a prescribed kind. That's why the EPA requires the following text on all product labels:

• Do not apply over cuts, wounds, or irritated skin.
• Do not apply to hands or near eyes and mouth of young children.
• Do not allow young children to apply this product.
• Use just enough repellent to cover exposed skin and/or clothing.
• Do not use under clothing.
• Avoid over-application of this product.
• After returning indoors, wash treated skin with soap and water.
• Wash treated clothing before wearing it again.

Labels on sprays must also say:

• Do not spray in enclosed areas.
• To apply to face, spray on hands first and then rub on face. Do not spray directly onto face.

If you decide to use DEET, do follow these instructions for safety.

Age of user: Notwithstanding the special precautions recommended for children above, the EPA has approved DEET for use on children of any age at any concentration.

The American Academy of Pediatrics recommends more caution. It advises no DEET for infants under two months and a maximum concentration of 30% for children over two months (which, to reiterate, is a good cap for adults too). Duke University pharmacologist Mohammed Abou Donia says to avoid DEET on infants altogether for two reasons. First, a baby's skin is too thin to act as a barrier to absorption. Second, babies cannot metabolize chemicals as well as older children and adults.

As many substances that affect kids can also affect fetuses, pregnant women may want to consider the possible risks to children in connection with their own use of DEET.

NEWER—AND NATURAL—ALTERNATIVES

Picaridin: Picaridin has been widely used in other parts of the world, and has been available in the U.S. in a variety of brands since 2005. Structurally based on chemicals in pepper, it appears to interfere with the mosquito's ability to smell its prey. The chemical is extremely effective for some species of mosquito (including important disease-carrying mosquitoes such as A. aegypti), but is less effective for other species that don't appear to rely on smell, so overall it may be somewhat less effective than DEET. A 20% Picaridin formulation has been shown to repel mosquitoes for 8-10 hours.

Picaridin is much less irritating to the skin than DEET, so it might be a better choice for people with sensitive skin. It has very low toxicity and does not appear to cause adverse neurological or reproductive effects. Nor does it cause cancer in animals. It also lacks the unpleasant odor of DEET.

Natural alternatives: Studies have shown that oil of lemon eucalyptus and soy oil perform comparably to many DEET-based products. A recent Consumer Reports study found one commercial preparation with lemon eucalyptus was effective for seven hours. Note that use of lemon eucalyptus is not advised on children under three. It is important to remember in this context that the fact that a chemical is natural, not synthetic, does not necessarily mean it is safe.

Other natural repellents have been shown in tests to be very short-lasting. Some lose efficacy in less than 20 minutes and cannot be considered practical options.

PREVALENCE OF BUG-BORNE DISEASES

Any possible short- or long-term risks of DEET—or any bug repellent—have to be weighed against the known, serious effects of diseases carried by insects and ticks, including West Nile virus, Lyme disease, dengue fever and malaria. If you live in or are traveling to an area where these diseases are prevalent, make sure you have a plan for protection and follow it.

BEYOND INSECT REPELLENTS

To avoid a mosquito problem in your own yard, get rid of standing water. This is where mosquitoes breed.

Check your local mosquito forecast and stay indoors or in a screened porch when levels are expected to be high.

Keep yourself well covered when you venture outside at buggy times. Wear socks, long pants and long-sleeved shirts made of heavy fabric that mosquitoes can't bite through. Then you only need repellent (if you choose to wear it) on your face and hands.

Proper clothing is really a must when it comes to avoiding ticks that may cause Lyme disease—whether or not you use a repellent. Not only do you need full coverage, but the clothing should be light in color and you should tuck your pants into your socks. Check periodically for ticks on your clothes while you're out and then check your body when you get home. Removing a Tick. Dry the clothes you wore on your outing in a hot dryer for 20 minutes.

When traveling in areas where you may be exposed to disease-carrying mosquitoes indoors, sleep under mosquito netting.

—Sheryl Eisenberg


Chemical under magnifying glass

CommentSubscribe

Join me on Facebook
Share

Related TGLs


Pet Protection Pet Protection
Keeping pets free of pests, safely

A Greener Lawn A Greener Lawn
No pesticides needed

Mothballed Mothballed
A natural approach to moths

Pollution in People Pollution in People
Keeping chemicals out of your body


On This Topic


THE BEST ALTERNATIVES TO DEET are Picaridin, lemon eucalyptus oil and soy oil. In testing, all proved long-lasting and effective. Research shows citronella, a natural repellent that has long been used in skin formulations and candles, to lose efficacy in a very short span of time.


Proper clothing
KEEP COVERED. It is not the advice most people want to hear when the weather is warm, but you can minimize the need for repellents, synthetic or otherwise, by wearing closed shoes, along with a long-sleeved shirt, long pants and socks, all made of thick material that bugs can't bite through.



FIND A PRODUCT. Use the EPA's Insect Repellents Search Tool to find products with a particular active ingredient, such as oil of lemon eucalyptus. (The search tool is halfway down the EPA page, so you'll need to scroll.)

Wondering what's in a product you already have or see in the store? Look for the active ingredients listed on the label. Sometimes, the chemical name is used instead of the common English name. Here's the translation:

• DEET is N,N-diethyl-m-toluamide or N,N-diemethylbenzamide.
• Picaridin (aka Icaridin) is 2-(2-hydroxyethyl)-1-piperidinecarboxylic acid 1-methylpropyl ester.
• Oil of lemon eucalyptus (aka PMD) is para-Menthane-3,8-diol. The reason it may appear with a chemical name despite being a natural substance is that a synthesized version is used in most commercial preparations.



AVOID DUAL USE PRODUCTS combining DEET with sunscreen. It is necessary to apply sunscreen more often than DEET so you will end up with too much exposure to DEET.



ARE SEIZURES CAUSE FOR CONCERN ABOUT DEET? Not for most folks. NRDC senior scientist Gina Solomon says that DEET lowers the seizure threshold, so it is not likely to cause seizures in healthy people, but could trigger a seizure in someone with an underlying propensity, or in a child with a fever.



Places where standing water might collect
Newly hatched mosquito
REDUCE MOSQUITO BREEDING SITES in your yard by clearing standing water on a regular basis. Mosquitoes do not need a lot of water to lay their eggs. The small overflow in a dish under a flower pot could be enough. Change outdoor pet water dishes daily (which is healthier for your pets anyway) and clean bird baths once or twice a week.



Resources


NRDC's Simple Steps
Keep Mosquitoes at Bay
Safe Repellents That Work?
Bug-Repellent Duds

EPA
Insect Repellents Search Tool
DEET

Centers for Disease Control
Mosquito Repellent
Travelers' Health Protection
Removing a Tick

CBS News
Safer Bug Spray: Natural Bug Repellents

Northwest Coalition for Alternatives to Pesticides
Plant-Based Mosquito Repellents

The Weather Channel
Mosquito Activity Forecast



More to Do

TGL Nature Map Switchboard Simple Steps
To share your favorite nature spots with other nature lovers on the TGL Nature Map, sign in first to your Google or Gmail account. Not sure how to add to the map? Get help here.


Sheryl Eisenberg is a writer, web developer and long-time advisor to NRDC. With her firm, Mixit Productions (mixitproductions.com), she brought NRDC online in 1996, designed NRDC's first websites, and continues to develop special web features for NRDC. She created and, for several years, wrote the Union of Concerned Scientists' green living column, Greentips, and has designed and contributed content to many nonprofit sites. Sheryl makes her home in Tribeca (NYC), where—along with her children, Sophie and Gabe, and husband, Peter—she tries to put her environmental principles into practice. No fooling.