ScienceDaily (Aug. 6, 2009) — The active ingredient in many insect repellents, deet, has been found to be toxic to the central nervous system. Researchers say that more investigations are urgently needed to confirm or dismiss any potential neurotoxicity to humans, especially when deet-based repellents are used in combination with other neurotoxic insecticides.
http://www.sciencedaily.com/releases/2009/08/090804193230.htm