[The prescription of repellents]

Repellents are chemical products designed to ward off insects. They are effective against a wide range of arthropods including mosquitoes and flies but not against bees and wasps. Choosing the proper repellent can be difficult because no single product repels all pests. This article compares the performance and toxicity of various repellents based on reports describing systemic, topical, or physical repellents made from natural or synthetic ingredients. Essential oils are the most common natural ingredient. Synthetic ingredients range from dimethyphtalate, ethylexanediol, and diethyltoluamide (DEET) to new molecules such as 35/35, piperidine, bayerepel, and KBR 3023. Our findings indicate that DEET, used as the gold standard in most studies, is still the most effective repellent. There is no synergy between any of these products but combinations (e.g. ethylhexanediol and DEET) can optimize protection. In conclusion we propose guidelines for prescribing repellents to achieve the required level of protection in function of the duration of exposure and benefit-to-risk ratio. Several recommendations are made on the safe use repellents for adults and children.