DEET is a chemical compound commonly used in insect repellents to protect against bites from mosquitoes, ticks, and other pests. Its full name is N,N-Diethyl-meta-toluamide, and it was developed by the U.S. Army in the 1940s. DEET works by interfering with the insects' ability to detect humans, making it less likely for them to land on or bite the skin. Products containing DEET come in various concentrations, typically ranging from 5% to 100%. Higher concentrations provide longer-lasting protection, but even lower concentrations can be effective for shorter periods. It is generally considered safe for use on skin when applied according to the instructions, although some people may experience skin irritation.