The most potent mosquito repellent in your house might be tucked away in the cat's toy mouse. Insect toxicologists Joel Coats of Iowa State University and Chris Peterson of the U.S. Forest Service study catnip, and their previous studies had confirmed folklore that catnip repels some insects. So the researchers decided to see what else it could do. They coated a paper disk with catnip's essential oil and placed the disk at the end of a glass cylinder containing about 20 mosquitoes. A solution containing just one tenth of 1 percent of catnip oil repelled more than half the mosquitoes. DEET, the most common chemical repellent in bug sprays, is ineffective at such low concentrations.
Coats doesn't know why catnip works, but he suspects the oil will prove useful on clothes or bed netting. Given some concerns about DEET's safety, says Coats, "I think people are ready for alternatives." Next, he and Peterson plan to see if the Osage orange, an inedible fruit that repels cockroaches, works on mosquitoes.