Deet insect spray repels insectsThe CDC (Center of Disease Control and Prevention) recommends using insect repellents with the following active ingredients: DEET, IR3535, oil of lemon eucalyptus (OLE), or Picardin (KBR 3023).  A repellent with one of these active ingredients has to be registered with the EPA to make sure it has been tested and approved for human safety. The CDC warns against using "pure" oil of lemon eucalyptus (the essential oil) as it has not been tested by the EPA for safety and effectiveness.

The most effective repellents contain DEET (N,N-diethyl-m-toluamide) to repel pests like mosquitoes and ticks. DEET insect spray has been tested against a variety of biting insects and has been shown to be very effective. The more DEET a repellent contains the longer time it can protect you from mosquito bites. A higher percentage of DEET in a repellent spray does not mean that your protection is better, just that it lasts longer.