To find safe, effective natural insect repellents that are an alternative to DEET, you have to scratch below the surface. In addition to the usual greenwashing and other marketing hype, you'll find lots of conflicting information as well as some rather sketchy, fear-based "scientific reports."
There are two main types of repellents: conventional repellents containing synthetic chemical compounds, and "biopesticide" repellents that contain natural, plant-based compounds.
Of the four ingredients widely acknowledged as effective insect repellents, the first two are conventional repellents, and the last two are considered biopesticides:
- Lemon eucalyptus oil
There are also dozens of other plant-based oils that are touted as effective repellents (citronella oil, rosemary oil, cinnamon oil, etc.). Most studies have shown that these don't work well or need to be reapplied so often -- every 20 minutes in some cases -- that they're just not practical to use. You can sometimes find these plant-based oils added to repellents that contain other, more effective ingredients.
How Safe Are Conventional Insect Repellents?
DEET has been used by the general public as a bug repellent since 1957. As long as it's used as directed, DEET has been considered safe by groups like the American Academy of Pediatricians and the U.S. Centers for Disease Control and Prevention.
But the "use-as-directed" directions for use require that DEET be washed off the skin after coming indoors, as well as other specifics (don't get near mouth or on children's hands, etc.). There are reports of adverse reactions to DEET, including seizures and skin rashes, though these are rare. There is also some evidence that extensive, long-term exposure to DEET is associated with higher rates of insomnia, mood disorders and impaired cognitive function.
An August, 2009, study from France found that DEET may have a toxic effect on the nervous systems of mammals as well as insects. This disturbing discovery calls into question the presumed safety of DEET, the world's most widely used insect repellent.
Picaridin is another conventional insect repellent; after years of successful use in Europe and Australia, it was introduced into the U.S. in 2005. Highly effective and widely recognized as safe, picaridin is the active ingredient in Cutter Advanced Insect Repellent and Avon Skin-So-Soft Bug Guard Plus Picaridin.
Both picaridin and DEET are believed to have negligible effects on the natural environment. One advantage these two chemical compounds have over some plant-based insect repellents is their effectiveness at repelling ticks, including those that carry Lyme disease.