The Centers for Disease Control and Prevention (CDC) recommends using products that have been shown to work in scientific trials and that contain active ingredients which have been registered with the U.S. Environmental Protection Agency (EPA) for use as insect repellents on skin or clothing.

When the EPA registers a repellent, they evaluate the product for efficacy and potential effects on human beings and the environment. EPA registration means that EPA does not expect a product, when used according to the instructions on the label, to cause unreasonable adverse effects to human health or the environment.

Of the active ingredients registered with the EPA, the CDC believes that two have demonstrated a higher degree of efficacy in the peer-reviewed, scientific literature. Products containing these active ingredients typically provide longer-lasting protection than others:

• DEET (N,N-diethyl-m-toluamide)
• Picaridin (KBR 3023)

Oil of lemon eucalyptus [active ingredient: p-menthane 3,8-diol (PMD)], a plant- based repellent, is also registered with EPA. In two recent scientific publications, when oil of lemon eucalyptus was tested against mosquitoes found in the United States it provided protection similar to repellents with low concentrations of DEET.