"The CDC is pushing hard to develop a completely natural insect repellent made from a chemical called nootkatone, which is found in Alaska yellow cedar trees and citrus fruit.

[Scientist Marc] Dolan says nootkatone 'is nongreasy, dries very quickly, and it has a very pleasant, citrus-y grapefruit odor to it.'

He recently demonstrated its effectiveness as a mosquito repellent, rubbing some on his hand and then sticking it into a cage containing 50 hungry mosquitoes. When he holds the treated hand near mosquitoes, they try to get away in the opposite direction as fast as they can."

Richard Knox reports for NPR's Morning Edition April 18, 2011. [2]