The evidence for DEET (N,N–diethyl-m-toluamide) from trials is limited and based on small randomized controlled trials (RCTs) with non-clinical outcomes. Nevertheless, decades of experience of using DEET has led to a consensus that it is the most effective insect repellent for malaria prophylaxis. DEET can be used at a concentration of 50%. It can also be used in all stages of pregnancy, for breastfeeding women, and in children over the age of 2 months.

• Trials have compared DEET with other insect repellents and shown DEET to have a longer duration of protection.
• A trial involving 15 volunteers compared DEET (4 types of formulations up to 23.8% concentrations) with ethyl butylacetylaminopropionate, wrist bands impregnated with insect repellents, and a moisturiser with repellent properties. The results showed DEET to have an average duration of protection of around 5 hours, the ethyl butylacetylaminopropionate protected for about 23 minutes, and the others for less than 20 minutes [Fradin and Day, 2002].
• In trials, the insect repellents IR3535 (ethyl butylacetylaminopropionate), IR3023 (picaridin), and lemon eucalyptus (p-methane 3,8 diol) have been proven to be well tolerated for mosquito-bite prevention in humans [Chiodini et al, 2007].
• Trials have suggested that:
• Picaridin (IR3023) has a similar effectiveness to DEET [Badolo et al, 2004; Costantini et al, 2004].
• Lemon eucalyptus (p-methane 3,8 diol) appears to be comparable to 15% DEET concentrations [Govere et al, 2000].
• A number of case series have reported systemic reactions with DEET. Fourteen case studies highlight adverse skin reactions resulting in contact urticaria and dermatitis. However, the general consensus is that DEET is suitable for use in anyone over 2 months of age [Croft, 2006].