Air Date: Week of September 7, 2001

Living on Earth's Diane Toomey reports on Catnip, an herb that is known to attract cats, of course. Now researchers have discovered that it might also be a mosquito repellent.

Transcript

CURWOOD: Coming up, it wasn't just the Conquistadors: the link between weather and disease in the deaths of native Mexicans centuries ago. First, this health note from Diane Toomey.

TOOMEY: Any cat owner will tell you, put out the catnip and the cats will come. But the herb seems to have just the opposite effect on mosquitoes. Entomologists from Iowa State University discovered this when they tested the oil found in catnip for its insect repellent qualities. They coated half a glass tube with the oil, then filled it with mosquitoes. After ten minutes about 80% of the bugs moved away from the site of the tube treated with the oil. The same test was done using DEET, the compound found in most commercial insect repellents. In that case, only about 55% of the mosquitoes retreated from the coated side of the tube. What's more, only a tenth of the amount of catnip oil is needed to produce the same effect as DEET. No one knows if the oil would be effective if applied to human skin, and, since this is the same ingredient that makes catnip irresistible to cats, users might be substituting one problem for another.

Researchers don't know why mosquitoes shy away from catnip oil. They think the substance might act as an irritant, or maybe the mosquitoes just don't like the smell. That's this week's Health Update. I'm Diane Toomey.

CURWOOD: And you're listening to Living on Earth.

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