Aug. 28, 2001 -- Your cat's favorite herb may become yours too if you enjoy spending time in the great outdoors. The essential oil of catnip may be 10 times more potent than standard insect repellents in fighting off mosquitoes.
Researchers at Iowa State University compared the essential oil of catnip, called nepetalactone, to Diethyl-m-toluamide (DEET), which is the main ingredient in many commercial insecticides. According to a report at the 222nd national meeting of the American Chemical Society currently underway in Chicago, catnip oil was more effective than DEET in repelling mosquitoes.
"Natural alternatives are becoming available to repel mosquitoes," says researcher Joel R. Coats, PhD. "Our lab tests show the essential oil of catnip would be effective in repelling mosquitoes when sprayed on clothing or mosquito netting. We think it would also be effective if rubbed on your skin, but we haven't actually done that test yet." Coats is professor of entomology and toxicology and chairman of the department of entomology at Iowa State University in Ames.
"People are starting to expect that we use safer compounds to control insects," Coats says. "There have been reported health problems with DEET. While they are very unusual, they do include brain swelling in children, anaphylactic shock, low blood pressure, and one report of death."
He believes catnip oil would also protect pets and large animals. "The oil is also effective in repelling house flies and cockroaches. However, I don't know whether the herb itself would be an effective repellent, since the oil is much more concentrated."
Catnip oil is extracted from an aromatic herb, nepeta cataria. Catnip has a centuries-old reputation as a soothing herbal tea, used for coughs, indigestion, and menstrual cramps, and to promote drowsiness. The oil is available from companies that sell essential oils for aromatherapy and herbal treatments.
Recent cases of West Nile virus have prompted renewed interest in better ways to control and repel mosquitoes. While the Iowa tests were carried out on the mosquito that carries yellow fever, "We think it is also likely to repel the mosquitoes which carry West Nile," Coats says.
"It's always important for us to look for newer, more effective strategies, and this idea certainly sounds interesting," says Kimberly Thompson, ScD, an assistant professor of risk analysis and decision science at Harvard University School of Public Health in Boston. She also recommends another way, in addition to repellent, to combat mosquitoes of any kind. "If you're going to be out in the early evening or early morning when mosquitoes are most active, wear long-sleeved shirts."
Mark Brown, PhD, an associate professor of entomology at the University of Georgia in Athens, has another suggestion. "The key to mosquito control is personal responsibility," he tells WebMD. "Get rid of standing water around your house and in your neighborhood."