Think twice before using insect repellants containing the common active ingredient, DEET. Recent studies have found DEET to be toxic to the central nervous system in both mammals and insects. Although DEET is very powerful at repelling insects, the potential side effects are much too dangerous to ignore.One of the most common active ingredients found in synthetic insect repellants is DEET (N, N-diethyl-meta-toluamide). DEET is a powerful insecticide used in over 400 products. Discovered in 1953, DEET is now the most common active ingredient found in insect repellants. Every year, one-third of all Americans cover themselves with DEET-containing products. This powerful ingredient repels most insects, particularly mosquitoes. With prevalent mosquito-borne diseases such as West Nile Fever and Lyme Disease, repellants containing DEET have become even more popular.Before slathering on the DEET containing products though, we should take a look at some of the possible side effects of such chemicals on the human body. Research at Duke Medical Center in North Carolina found that prolonged exposure to DEET can impair the brain, resulting in problems such as muscle weakness, lack of coordination, and difficulty with memory and cognition.In the latest study, French scientists Vincent Corbel and Bruno Lapied discovered that DEET is toxic to the central nervous system. They found that DEET inhibits the activity of the key central nervous system enzyme, acetycholinesterase in both insects and mammals. These neurotoxic effects of DEET are particularly harmful when used in combination with other insecticides, such as organophasphate and carbamate, which magnifies the toxicity. Unfortunately, these insecticides are very often combined with DEET in insect repellants.Natural, effective and safe alternatives to DEET are available. Insect repellants can be made with all natural and organic ingredients that are not unsafe for humans. Many products are made from naturally occurring sources that repel certain insects. These natural insect repellants are made primarily from essential oils derived from plant sources. Most natural repellents are just as effective as DEET, and they have a huge advantage because the ingredients are not toxic to humans.Repellents which contain the natural oil eucalyptol have been found to be a highly effective and nontoxic alternative to DEET. Many natural insect repellants also contain the aromatic oil of citronella, which has been approved by the US Environmental Protection Agency as a non-toxic pesticide. Plants such as lemon grass have also proven effective against mosquitoes.Although DEET is very effective as an insect repellant, its safety is questionable. DEET is a moderate pesticide and studies have shown that it may not be suitable for use in and around water sources. Natural, organic insect repellants that don't contain harmful artificial ingredients are available, and are just as effective. Therefore, the health concerns from use of DEET far outweigh its effectiveness against insects.