UNIVERSITY PARK, Pa. -- With the spread of West Nile virus and Lyme disease, it's a good idea to take precautions to lower your risk of pest-borne illnesses. The proper use of repellents is one of the most effective defenses against mosquito and tick bites, says an expert in Penn State's College of Agricultural Sciences.

"We can try to avoid or eliminate environments where mosquitoes and ticks live, but it's virtually impossible to totally eliminate our exposure to these pests," says Steven Jacobs, extension entomologist. "Repellents, when used properly, can be a safe and effective preventive measure."

Repellents are chemicals that can be applied to clothing or exposed skin to protect against biting arthropods. Jacobs says repellents containing N,N-diethyl-meta-toluamide -- commonly referred to as DEET -- are effective in repelling mosquitoes, ticks, fleas and chiggers. "But people differ in their attractiveness to mosquitoes and other pests, so the effectiveness of any repellent may vary from person to person," he adds.

For most adults, products containing 10 to 35 percent DEET will provide adequate protection for one to five hours under most conditions. In general, the higher the concentration of DEET, the longer the protection lasts. Jacobs says the higher concentration products are best suited for use in areas where there are high numbers of mosquitoes or other pests, or where high heat and humidity cause loss of repellent from the skin due to excessive perspiration.

"It's wise to use the lowest concentration of DEET that you've found to be personally effective," Jacobs says. "And the American Academy of Pediatrics recommends that repellents used on children contain no more than 10 percent DEET."

Jacobs offers a few guidelines on the safe application of repellents:

--Before using any product, read and understand the directions and cautions on the label.

--Don't spray repellent in an enclosed area or near food, and don't inhale aerosol formulations.

--Repellents should not be applied to infants or used by pregnant women.

--Use just enough repellent to lightly cover exposed skin and clothing. Never apply repellents to cuts, wounds or inflamed and irritated skin. Don't apply beneath clothing.

--To apply repellent to your face, first dispense it onto your palms and rub your hands together. Then apply a thin layer to your skin.

--Don't allow children to apply DEET by themselves. Don't apply repellent directly to a child's skin. First, apply it to the palms of your own hands and then apply it to the child. Don't apply repellent to children's hands because they may touch their eyes and mouth.

--After applying repellent, wipe or wash it from your hands.

--Avoid prolonged or excessive use of DEET.

--Once indoors, wash all treated skin and clothing with soap and water.

--A small segment of the population may be sensitive to DEET or other repellents. If you suspect that you or your child is reacting negatively to a repellent, discontinue its use, wash treated skin and call the local poison control center. If you must see a doctor, take the repellent with you because the label will provide additional medical information.

For more information on DEET, contact the National Pesticide Telecommunications Network at (800) 858-7378, or visit the organization's Web site at http://ace.orst.edu/info/nptn/.

More information also is available in the Penn State Cooperative Extension fact sheet, "Using Insect and Tick Repellents Safely." Single copies are available free of charge at Penn State Cooperative Extension county offices. The fact sheet also is available on the Web at http://pubs.cas.psu.edu/freepubs/pdfs/uo211.pdf.

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EDITORS: Printable infographics to illustrate this story are available for downloading at http://aginfo.psu.edu/news/may03/repellent1.pdf and http://aginfo.psu.edu/news/may03/repellent2.pdf.

Contact:

Chuck Gill cdg5@psu.edu 814-863-2713 814-863-9877 fax #144