WEDNESDAY, Aug. 29, 2001 (HealthDayNews) -- Catnip, the plant that drives cats wild, may soon have another use: mosquito repellent.
New research has found the essential oil in catnip was more effective in keeping mosquitoes away than DEET, the chemical used in most commercial insect repellents.
Researchers from Iowa State University put groups of 20 mosquitoes into a two-foot glass tube, half of which was coated in a compound that contained 1 percent nepetalactone, the oil in catnip that gives the plant its characteristic odor.
After 10 minutes, only an average of 20 percent of the mosquitoes remained on the side treated with the nepetalactone. When researchers did the experiment again using a more diluted compound -- 0.1 percent nepetalactone -- only 25 percent of the mosquitoes remained.
Researchers repeated the test using similar amounts of DEET, the trademarked name for diethyl-m-toluamide. After 10 minutes, 40 percent to 45 percent of the mosquitoes remained on the treated side.
"Our goal is to find a safer alternative to DEET, and with catnip, we may have found it," said Joel Coats, a professor of entomology and toxicology at Iowa State University.
There have been a few cases of people dying after having severe allergic reactions to DEET, Coats said.
The research was presented this week at the national meeting of the American Chemical Society in Chicago.
In the laboratory, repellency is measured on a scale ranging from plus-100 percent for highly repellent to minus-100 percent for a strong attractant. According to the Iowa researchers, catnip's rating ranged from plus-49 to plus-59 percent at high doses and plus-39 to plus-53 percent at low doses. DEET's repellency was about plus-10 percent.
The makers of DEET are not convinced.
Laboratory tests tell little about the effectiveness of a product in the great outdoors, said David Gleeson, president of Morflex, the Greensboro, N.C., company that produces DEET.
Mosquitoes are attracted to humans because we emit carbon dioxide and heat, Gleeson said. For 50 years, DEET has been considered the "gold standard' of insect repellents, because it is safe for nearly everyone to use, long-lasting and highly effective, he added.
"We've run field tests against all types of products, both chemical and natural, and DEET is by far the superior product," Gleeson said. "For someone to make a claim that they have a product that is more effective then DEET that hasn't been tested in field trials would certainly be a subject of debate as to how valid that claim is."
Catnip is a perennial herb in the mint family. Native to Europe, it was probably brought to the United States in the 18th century, Coats said, and now grows wild throughout much of the country.
Although primarily used on toys for cats, catnip is also used to make tea, as a meat tenderizer and in alternative medicine for fevers, colds, cramps and migraines.
"It also has a long-standing reputation in folk medicine as being an insect repellent," said Coats, whose research team found in earlier research that catnip repels cockroaches.
Researchers say they do not know why cats love it -- and mosquitoes hate it.
Catnip was tested as a repellent against the Aedes aegypti mosquito, one of several species found in the United States. Aedes aegypti carries yellow fever in Africa and South America, according to the CDC.
Vaccines and mosquito control programs have wiped out the disease in the United States, although there have been a few isolated reports of unvaccinated travelers returning with the disease.
Coats believes catnip will repel all species of mosquitoes.
If nepetalactone is found to be safe, it could be easily distilled for use in a commercial product, he said, although no animal or human tests have been scheduled yet.
What To Do
To read more about catnip, check out How Stuff Works. You can also
read more about DEET here.
To learn about the health dangers of mosquitoes and how to keep them under control, visit the Environmental Protection Agency.
