The popular bug spray known as DEET blocks insects from picking up the smells on humans that would otherwise register as "food," a new study says.
The finding could help solve the 50-year-old mystery of exactly how the powerful human-made repellent keeps mosquitoes and other pests at bay.
Many consumers have long believed that strongly scented DEET also smells bad to insects and causes them to steer clear.
But according to the new research, DEET temporarily destroys an insect's sense of smell by hindering the function of certain odor receptors.
"From far away they start smelling you," said study co-author Leslie Vosshall of the Rockefeller University in New York City.
"Then they encounter a cloud of DEET and their olfactory system is jammed and they can't find you."
Powerful and Mysterious
Scientists at the U.S. Department of Agriculture invented DEET in 1958, but at the time no one fully understood how it worked.
"They found it more or less by trial and error," Vosshall said.
"I assume they found compounds off the shelf and tested them for their ability to make mosquitoes go away. Then they tinkered with molecules to make them safer and more effective."
(Related news: "Frog 'Juice' May Be Next Big Bug Repellent" [July 24, 2006].)
Morflex, Inc., the world's largest DEET manufacturer, estimates that about 200 million people around the globe use the repellent each year.
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