N,N-diethyl-meta-toluamide. The active ingredient in many insect repellant products:
liquids,
lotions,
sprays, etc. Americans love to use it: there's a million pounds of it manufactured and applied each year. Trade names for products include Autan, Delphene, Detamide, Deltamid, Flypel, m- Delphene, Meta-Delphene, Naugatuck Det, and Off.
It was developed and patented by the U. S. Army in 1946 for use by military personnel in insect-infested areas. It was registered for use by the general public in the U. S. in 1957.
While it has been shown to be effective in repelling ticks that carry Lyme disease and mosquitoes that may carry encephalitis or West Nile virus, you're better off applying DEET to your clothes rather than your skin, as it is absorbed quickly and spread throughout the body. By the way, DEET is a suspected neurotoxicant, liver toxicant, respiratory toxicant, and skin toxicant. "Can cause central nervous system disturbances" says the Material Data Safety sheet. "Mutagenic data." Yikes. Read application instructions carefully. You really don't want to apply more of this stuff than you have to.