How DEET Works

Insects like mosquitoes locate us through their sense of smell, not sight. The odors­ in our sweat and breath are extremely attractive to them. Specifically, carbon dioxide, lactic acid and an alcohol-based compound called 1-octen-3-ol ar­e the main allure. The olfactory system of an insect contains odorant receptors, used to recognize the smell of prey. DEET interferes with these receptors, but scientists aren't sure exactly how. Does DEET smell bad to mosquitoes? Or does it simply make them unable to smell at all? Research results vary.

A study in 2008 showed that DEET targets certain odorant receptors in the insect, confusing its olfactory system and therefore "blinding" the bug to the odor that usually attracts it to us [source: Science Daily]. So, if this is true, DEET isn't actually a repellent. It's more like an invisibility cloak. However, a more recent study suggests that mosquitoes can actually smell DEET. A University of California Davis study showed that mosquitoes avoid DEET because they think it stinks [source: Fountain].

DEET is available to the consumer in various forms. In fact, the­ U.S. Environmental Protection Agency currently registers 39 companies with about 140 products containing DEET [source: EPA]. DEET products are available as liquids, lotions, sprays, and impregnated materials like wristbands or wipes. These products are all for direct application to the skin.

So how much DEET do you need to rub onto your skin to make yourself unattractive or invisible to biting insects? Currently, DEET skin application products are available in concentrations from four to 100 percent [source: EPA]. A higher concentration of DEET doesn't mean it's more effective -- it just means it lasts longer. The more DEET a product contains, the longer it will protect you from insects. For example, if you plan to do some gardening in the yard for only an hour or so, a product with 5 to 7 percent DEET should be enough. For a longer, more intense outdoor experience like fishing or hiking, 25 to 30 percent is a better choice [source: SE Johnson].

That said, the Centers for Disease Control and Prevention (CDC) states that any concentration more than 50 percent doesn't offer any added protection [source: CDC]. In fact, Canada limits all consumer DEET products to a concentration of 30 percent or less [source: Health Canada]. If you need longer protection, labels recommend that you simply reapply once the repellent stops working.

The EPA doesn't restrict DEET concentration for children, saying there's no data to suggest any negative effects [source: EPA]. However, the American Academy of Pediatrics recommends using DEET products only on children older than two months and to keep it away from their hands, eyes and mouths [source: AAP].

Many people do feel DEET is dangerous and opt not to use it on themselves or their children. We'll look at DEET side effects and controversies on the next page.

As wit­h most chemical compounds, DEET doesn't come without warnings or side effects. First, let's take a look at how DEET affects the environment.

The U.S. Environmental Protection Agency (EPA) reregistered DEET in 1998 to ensure it conformed to today's more stringent standards (rather than the 1950s standards). Because DEET is applied to the skin and not directly on plants or wildlife, its impact on the environment is minimal. However, the EPA shows DEET as slightly toxic to birds, fish and aquatic invertebrates. It's virtually nontoxic to mammals. The EPA currently rates DEET as Toxicity Category III, the second lowest of four categories -- or "slightly toxic" [source: EPA].

So, is DEET bad for you? The answer isn't totally clear. Overuse of DEET can have lethal consequences. Even so, data from 1961 to 2002 shows only eight DEET-related deaths. Three were from deliberate ingestion, two from dermal (skin) exposure and three were children receiving heavy and frequent applications of DEET [source: death [source: ATSDR].

You hear rumors that DEET causes cancer. This may partly be due to the fact that people confuse DEET with DDT, a known carcinogen. In truth, scientists have not established a direct link between DEET and cancer. The Centers for Disease Control and Prevention (CDC) classifies DEET as a group D carcinogen -- meaning it's not classifiable as to human carcinogenicity. In simple terms, that means that they can't say it causes cancer, but they can't say it doesn't, either.

For at-a-glance information, the activist group Beyond Pesticides keeps its own list of documented DEET health and environmental effects:

[source: Beyond Pesticides]

Some researchers have even tied DEET to the mysterious Gulf War Illness suffered by ­many veterans of the 1991 war. Numerous soldiers reported symptoms­ like chronic fatigue, headaches, dizziness, loss of muscle control, memory issues, and muscle and joint pain. Studies in the mid-1990s showed that a combination of pesticides, including DEET, and an anti-nerve gas agent caused similar symptoms when tested on animals and insects [source: Waters].

That said, you're probably wondering how you can use DEET safely. DEET is an important weapon in the fight against mosquito- and tick-borne illnesses, so it's definitely got its value -- you just have to make sure you use it according to the label's directions. The U.S. Environmental Protection Agency requires companies to list precautions on their product labels. These labels provide important information on how to handle and apply the product. The following are some general guidelines about using products that contain DEET:

After reading all this, you might be wondering if DEET is worth the risk. But studies suggest that DEET is still the most effective insect repellent available [source: malaria, West Nile or yellow fever, the benefits of DEET far outweigh the risks. But it's up to you to weigh the facts and make your own decision.

Kids play outside a lot, and you don't want them coming in with­ itchy welts all over their bodies. But is it safe to cover your child's skin in DEET?

It is safe -- as long as you're careful about how you apply the chemical. When using DEET on or around children, use the following precautions:

If you notice an adverse reaction, it's safest to contact Poison Control for advice. You can gently wash the affected area with soap and water, and bring the insect repellent with you to the medical office.