Background. Prevention of mosquito bites is an important part of a malaria prevention strategy. The insect repellent N,N-diethyl-m-toluamide (DEET) is the globally most widely used product for this purpose. DEET is considered very effective and is the gold standard for mosquito repellents. However, there are concerns related to possible toxic effects, most notably seizures or other neurologic symptoms, particularly in children. In Norway, the sale of products containing more than 20 % DEET is prohibited, whereas higher concentrations are allowed and recommended in Canada, the United Kingdom and the United States.
Objective. To determine the best practice for DEET use for the purpose of malaria prevention, based on current liturature, with an emphasis on a trade-off between optimal effect and avoidance of adverse reactions. Also, specifically to determine whether the Norwegian limitation of 20 % DEET maximum is warranted.
Methods. The project is based on original and review articles in medical journals, obtained through literature searches in the databases MEDLINE/PubMed and EMBASE. The search terms “DEET” and “concentration” were used, and combined with keywords such as “efficacy”, “repellency”, “effect”, “adverse effects” and “toxicity”.
Results. The duration of action of DEET is directly dependent on the concentration of DEET applied to the skin. Mosquitoes of the genus Anopheles have a significantly higher tolerance to DEET than mosquitos of the genera Aedes and Culex. Based on this, and other factors such as climate that influence the duration of action of DEET in tropical areas, a concentration of 20 % may be too low to provide adequate protection against malaria vector mosquitoes. There is no evidence that higher concentrations of DEET lead to a higher risk of toxicity, although pharmacological studies suggest that concern should be used when applying DEET to children. Products that deliver DEET through a polymer or liposphere formulation may reduce the amount of DEET absorbed and thereby the risk of systemic adverse effects, although these products have not been systematically evaluated.