Chemical in bug spray works by masking human odors

Scientists say DEET, long a mystery, inhibits the receptors that allow insects to smell their human prey

Fifty years have passed since the United States Department of Agriculture and the U.S. Army invented DEET to protect soldiers from disease-transmitting insects (and, in the process, made camping trips and barbecues more pleasant for the rest of us civilians). But despite decades of research, scientists still didn't know precisely how it worked. Now, by pinpointing DEET's molecular target in insects, researchers at Rockefeller University have definitively shown that the widely used bug repellent acts like a chemical cloak, masking human odors that blood-feeding insects find attractive. The research, which will be published in the March 13 issue of Science Express, now makes it possible not only to systematically improve upon the repellent properties of DEET but also to make it a safer chemical.

"For all these years, there were a lot of theories but no consensus on how DEET worked," says Leslie Vosshall, head of the Laboratory of Neurogenetics and Behavior. "Does it smell bad to mosquitoes or does it blind them to odors" It was a great unsolved problem."

Mosquitoes are strongly attracted to odors in human breath and sweat, including carbon dioxide, lactic acid and an alcohol-based compound called 1-octen-3-ol. Different receptors within their olfactory system detect these odors, among others, and lead them to their prey. DEET simply interferes with the proper functioning of odorant receptors, making the hunt for a tasty meal all the more difficult.

But this interference is selective.