Dear EarthTalk: Is DEET natural and is it safe to use topically as a mosquito repellent? And which formulations and concentrations are recommended?
-M. Frey, Milwaukee, WI
DEET (short for “diethyltoluamide”) is a synthetic compound invented by the American army in 1946 that can be applied topically to repel mosquitoes, ticks, fleas, chiggers, leeches and other pungent insects. Unlike other repellents that actually dissuade insects from smells they don’t like, or even kill them on contact, DEET makes the smell of pests more difficult, so they are more likely to leave us alone.
DEET has been available to the general public since the Army “released” it in 1957, and today it remains the majority of people’s choice repellents, with 90% market penetration in the United States. An estimated third of Americans use DEET to protect them from not only mosquito bites but also mosquito-borne diseases such as eastern equine encephalitis, West Nile virus, Zika virus and malaria, not to mention tick-borne diseases like Lyme disease and spotted fever in the Rocky Mountains.
DEET is not only effective, it is also convenient; it is sold in a variety of formulations (liquid, lotion, spray, towel) ranging from 5 to 99 percent. The US Environmental Protection Agency (EPA) considers DEET safe to use topically and has approved 30 companies to sell approximately 120 different DEET-based repellents online and on store shelves in the United States AND with 90% market penetration for repellents for insects, DEET appears to be here to stay.
Having said that, many of us are still concerned about DEET’s safety for our health and the environment. According to the Nonprofit Environmental Working Group (EWG), exposure to high concentrations of DEET can irritate the eyes and in very rare cases compromise the nervous system, with symptoms including convulsions, tremors and confused speech. But despite these risks, EWG recognizes that DEET is still probably the safest option for preventing insect-borne diseases.
If you want to use DEET, keep in mind that pediatricians generally recommend not to use it on infants up to two months, but to stick to concentrations of 10-30 percent for infants and young children. The higher the concentration of DEET you apply, the greater the longer-lasting protection you will get from mosquitoes. Consumer reports found that 99 percent of the DEET formulations provided up to 12 hours of protection while the lowest concentrations (20-34 percent) lasted 3-6 hours.
If you want to avoid DEET altogether, several effective alternatives are available, including Picaridin and PMD (eucalyptus lemon oil). Meanwhile, several vegetable oils (castor oil, cedar oil, lemongrass oil, clove oil, geraniol oil, lemongrass oil, peppermint oil, rosemary oil, soybean oil) are known to repel insects, but the EWG warns that many of these are not very effective, will not last long and may trigger the user’s allergic reactions on their own.
To decide what’s best for you and your family, given where you live and the risks for diseases transmitted by insects there, check out the search tool “Find the right repellent for you” which bases its recommendations on your inputs about what you are trying to fight, how long you will be out and potentially exposed, preference on active ingredients and even your favorite brand.
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