Until spring 2005, DEET-containing products have been the mainstay of effective mosquito repellents and have been the sole formulation recommended by the Centers for Disease Control and Prevention (CDC).   DEET-based repellents, while safe and effective, sometimes repel users due to an odor some people find offensive, an oily or sticky skin-feel, and a tendency to damage some plastics and synthetic fabrics.

Just in time for the 2005 West Nile virus season, the CDC has now added two new active ingredients to the recommended list.  These are picaridin (also known as KBR 3023) and oil of lemon eucalyptus [(p-menthane 3,8-diol (PMD)]. 

Picaridin has been in use for many years in mosquito repellents in Europe, Australia , Latin America and Asia , and it is recommended by WHO for malaria prevention.  Its effectiveness is comparable to DEET products containing a similar concentration of active ingredient.  In the U.S. , the first commercially-available product contains 7% picaridin and is being marketed under the name Cutter Advanced.  Other picaridin-containing products are expected to be available in the near future.

 Testing shows picaridin and DEET offer the longest-lasting protection.  DEET at a 24% concentration can provide protection for up to 5 hours.  Oil of lemon eucalyptus protects for shorter periods, similar to low concentrations of DEET.  CDC cautioned that oil of lemon eucalyptus should not be used on children under the age of three years and that it has not been tested against the mosquitoes that spread malaria and some other tropical diseases.  

A study published in 2002 in the New England Journal of Medicine found that perennial favorites citronella and Avon Skin-so-Soft, as well as DEET-impregnated wrist bands, offered only very short protection times.  Of the non-DEET products, a 2% soybean oil product provided up to 90 minutes of mosquito protection.  The NEJM article did not evaluate a picaridin product because it was not licensed for use in the U.S. at the time of the study.

Mosquito Repellent Precautions:

• Apply repellents to exposed skin, never under clothes
• Avoid use on wounds or irritated skin and do not apply to eyes or mouth
• Don’t spray directly on the face--instead spray hands first then carefully apply to face; apply sparingly around ears
• For children, adults should first apply the repellent to their hands then wipe it on the child’s skin
• And, of course, always read the label and follow instructions!

Permethrin is another effective insect repellent, but it should only be applied to clothing, shoes mosquito netting or camping gear, not directly to skin. Certain permethrin-containing products are registered with the EPA for this use. Permethrin can retain its effectiveness after repeated laundering, and some clothing and other commercial products are available pre-treated with permethrin.

External links:

• The CDC websites contain more information about the new recommendations at www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm and about DEET at www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm.                                               
• Information from the American Academy of Pediatrics about safe use of DEET for children can be found at www.aap.org/family/wnv-jun03.htm
• International travelers should consult the CDC Travelers’ Health website at www.cdc.gov/travel for more detailed recommendations on the use of insect repellents.