EarthTalk

Dear EarthTalk:

Is DEET natural and is it safe to use topically as a mosquito repellent? And which formulations and concentrations are advised?

-- M. Frey,

Milwaukee, WI

DEET (short for “diethyltoluamide”) is a synthetic compound invented by the U.S. Army in 1946 that can be applied topically to repel mosquitos, ticks, fleas, chiggers, leeches and other biting insects. Unlike other repellents which actually deter bugs with smells they don’t like—or even kill them on contact—DEET just makes it harder for pests to smell us so they are more likely to leave us alone.

DEET has been available to the...