DEET repels mosquitoes, ticks, and other arthropods when applied to the skin or clothing. Repellents with DEET should be used sparingly on children 2 through 6 years of age and not at all on infants younger than 2 years of age. A microencapsulated, sustained release formulation can have a longer period of activity than liquid formulations at the same concentrations. Length of protection also varies with ambient temperature, extent of perspiration, any water exposure, abrasive removal, and other factors. DEET is toxic when ingested.
High concentrations applied to skin can cause blistering.
Rare cases of encephalopathy in children, some fatal, have been reported after cutaneous exposure. Other neurologic side effects also have been reported. Toxicity did not appear to be dose-related in many cases and these might have been idiosyncratic reactions in predisposed individuals. However, a dose-related effect leading to irritability and impaired concentration and memory has been reported. If a reaction to insect repellent is suspected, travelers should be advised to wash treated skin and seek medical attention.