Dear EarthTalk: Is it true that the DEET used in most mosquito repellents is toxic? If so what problems does it cause? And what are some non-toxic alternatives for keeping mosquitoes at bay? -- Tom Pollack, Oakland, CA
DEET (N,N-Diethyl-meta-toluamide) is commonly known as the king of mosquito repellents, though not everyone is keen to slather it on their skin. A study conducted in the late 1980s on Everglades National Park employees to determine the effects of DEET found that a full one-quarter of the subjects studied experienced negative health effects that they blamed on exposure to the chemical. Effects included rashes, skin irritation, numb or burning lips, nausea, headaches, dizziness and difficulty concentrating.