DEET

N,N-Diethyl-meta-toluamide, also called DEET (/diːt/) or diethyltoluamide, is the most common active ingredient in insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection against mosquitoes, ticks, fleas, chiggers, leeches and many biting insects. N,N-Diethyl-meta-toluamide, also called DEET (/diːt/) or diethyltoluamide, is the most common active ingredient in insect repellents. It is a slightly yellow oil intended to be applied to the skin or to clothing and provides protection against mosquitoes, ticks, fleas, chiggers, leeches and many biting insects. DEET was developed in 1944 by Samuel Gertler of the United States Department of Agriculture for use by the United States Army, following its experience of jungle warfare during World War II. It was originally tested as a pesticide on farm fields, and entered military use in 1946 and civilian use in 1957. It was used in Vietnam and Southeast Asia. In its original form known as 'bug juice', the application solution for DEET was composed of 75% DEET and ethanol. Later, a new version of the repellent was developed by U.S. Army and the USDA. This incarnation consisted of DEET and polymers that extended the release of the DEET and reduced its evaporation rate. This extended-release application was registered by the EPA in 1991. A slightly yellow liquid at room temperature, it can be prepared by converting m-toluic acid (3-methylbenzoic acid) to the corresponding acyl chloride using thionyl chloride (SOCl2), and then allowing that product to react with diethylamine: DEET was historically believed to work by blocking insect olfactory receptors for 1-octen-3-ol, a volatile substance that is contained in human sweat and breath. The prevailing theory was that DEET effectively 'blinds' the insect's senses so that the biting/feeding instinct is not triggered by the chemicals present in the sweat and breath of humans or other animals. DEET does not appear to affect the insect's ability to smell carbon dioxide, as had been suspected earlier. However, more recent evidence shows that DEET serves as a true repellent in that mosquitoes intensely dislike the smell of the chemical. A type of olfactory receptor neuron in special antennal sensilla of mosquitoes that is activated by DEET, as well as other known insect repellents such as eucalyptol, linalool, and thujone, has been identified. Moreover, in a behavioral test, DEET had a strong repellent activity in the absence of body odor attractants such as 1-octen-3-ol, lactic acid, or carbon dioxide. Both female and male mosquitoes showed the same response. A 2011 structural study (PDB: 3N7H) revealed that DEET binds to Anopheles gambiae odorant binding protein 1 (AgamOBP1) with high shape complementarity, suggesting that AgamOBP1 is a molecular target of DEET and perhaps other repellents. A 2013 study suggests that mosquitoes can at least temporarily overcome or adapt to the repellent effect of DEET after an initial exposure, representing a non-genetic behavioral change. This observation, if verified, has significant implications for how repellent effectiveness should be assessed. Insect repellents containing DEET are the most effective. The concentration of DEET in products may range from less than 10 percent to nearly 100 percent. The benefits of DEET reach a peak at a concentration of 30 percent, the maximum concentration currently recommended for infants and children. DEET should not be used on children under 2 months of age.