Just How Bad Is DEET? A Look at the Common Insect Repellant Ingredient

We've all heard of DEET, the active ingredient in many common insect repellents, but there have been a few studies that raise questions about its safety. You've probably noticed that some mosquito repellents now sport the label "DEET-free" which likely prompts the question: Is DEET bad? And if so, why?

The threat of mosquito bites is very real, especially in certain outdoor careers and during the warmer seasons. However, DEET isn't necessarily the best way to keep the pests from attacking you during those barbecues and hikes. Here are some of the issues with DEET from environmental and health perspectives.

First of all, let's talk about what DEET actually is. DEET's chemical name, as the American Chemical Society explains, is N,N-Diethyl-m-toluamide. It's used as the active ingredient in many insect repelling products, and is seen as especially effective in warding off bites from ticks and mosquitoes. It works by masking humans' scent so that the insects don't detect us.

The EPA says that DEET was registered in 1957 for use by the general public to repel biting insects like mosquitoes. The EPA also says that about one-third of Americans use products containing DEET for the prevention of mosquito-borne illnesses such as West Nile Virus, the Zika virus, and malaria, as well as tick-borne illnesses such as Lyme disease and Rocky Mountain spotted fever.

There are some environmental hazards of DEET, but the EPA has deemed that the risks are not significant enough to warn people not to use these products. Outside Magazine discussed some of the reasons for warnings on DEET-based products.

One study on continental U.S. wastewater-polluted streams found DEET in 73 percent of sites sampled, indicating a risk of DEET's ability to move into the environment. A 1989 report in the Journal of Environmental Biology showed that DEET might accumulate in the organs of freshwater fish, potentially to the point of being lethal.

Despite these types of reports, some organizations claim that there isn't an environmental threat from DEET. For example, the World Aquaculture Society says the amount of DEET required to harm fish is so high that DEET is still "considered practically nontoxic." Plus, the Center for Biological Diversity says DEET isn't a hazard to any endangered species. We can certainly hope that's true.

We must also consider how DEET impacts human health. The Centers for Disease Control and Prevention (CDC) say there are occasional reports of negative reactions like "seizures, uncoordinated movements, agitation, aggressive behavior, low blood pressure, and skin irritation" in response to excessive DEET use.

Several organizations, including the U.S. Department of Health and Human Services and the International Agency for Research on Cancer, have not classified DEET as being a cancer-causing agent. The EPA has indicated that DEET is safe for human use, but only when used according to label instructions. That means spraying it on, never ingesting it.

Although DEET is approved for use in adults and children, be aware of the risks of large quantities or long periods of time, as Outside noted. For instance, one expert committee found that DEET may have caused symptoms of Gulf War Syndrome in military veterans. Another example is of National Park Service employees in the Florida Everglades who experienced muscle cramps and insomnia after using DEET products in large quantities on a daily basis.