What Bugs Mosquitoes? Smelling DEET

Aug. 22, 2008 -- So you spray bug repellent on your body and hope for the best. But do you know what really keeps mosquitoes from sipping on your blood?

A new study shows that mosquitoes actually posses a sense of smell located on their antennae.

"We found that mosquitoes can smell DEET and they stay away from it," says Walter Leal, PhD, professor of entomology at University of California Davis, in a news release.

He and his team carried out the study at the University of California, Davis.

The old theory of how insect repellents work was that DEET blocks the insect's ability to detect lactic acid from people, which acts as a mosquito magnet.

Instead, "DEET doesn't mask the smell of the host or jam the insect's senses. Mosquitoes don't like it because it smells bad to them," Leal says.

The researchers first identified a specific smelling neuron from mosquito antennae that was sensitive to DEET.

The researchers also tested mosquitoes with "sugar stations" sprayed with and without DEET.

Both male and female mosquitoes stayed away from the DEET areas.

Both mosquitoes eat nectar, but only the females suck blood for food.

They also found that DEET on human skin suppressed airborne chemicals that would normally be released from the skin. This effect may make skin less attractive to mosquitoes by blocking "the release rather than on the reception of chemical signals," write the researchers.

Lead study author Zainulabeuddin Syed, PhD, says in prepared comments that it was a breakthrough moment to discover the precise antennae neurons that detect the chemical cocktail known as DEET.

"I couldn't believe my eyes because it goes against conventional wisdom. So I repeated the experiment over and over until we discussed the findings in the lab," according to Syed.

In background information presented with the findings, authors write that DEET is "the gold standard" of mosquito repellents and is used by more than 200 million people around the world to keep mosquitoes at bay.

The findings could lead to better disease prevention, as mosquitoes are known for spreading diseases like West Nile virus, St. Louis encephalitis, and malaria.

The findings are published in the Aug. 18th edition of the Proceedings of the National Academy of Sciences.