Deet is useful for warding off mosquitoes and malaria - but researchers believe in small doses it could still be harmless.
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PARIS: One of the world's most common insect repellents acts on the central nervous system in the same way as some insecticides and nerve gases, says a new study.
Moderate use of the chemical compound, called deet, is most likely safe, the researchers say.
But experiments on insects, as well as on enzymes extracted from mice and human neurons, showed for the first time that it can interfere with the proper functioning of the nervous system.
Further study needed
The researchers say further studies are "urgently needed" to assess deet's potential toxicity to humans, especially when combined with other chemical compounds.
They added that their findings may also shed some light on Gulf War Syndrome, the name given to a complex and variable mix of neurological symptoms reported by tens of thousands of U.S. military veterans who served in the first Gulf War against Iraq in 1990/1991.
Developed by U.S. Department of Agriculture scientists just after World War II, deet has been available as a bug repellent for more than five decades.
Sold as lotions, creams and sprays in concentrations from five to 100%, it has been widely used not just by weekend campers but as a frontline barrier against malaria, dengue fever and other mosquito-borne diseases.
200 million people
Some 200 million people use deet-based products every years, according to the study, published in the British-based open-access journal BMC Biology.
Scientists still don't know exactly how the compound works on blood-seeking insects. Some say it blocks the sensory neurons that would be titillated by a potential meal, while others hypothesise that bugs are simply put off by the smell.
More surprising still, there is relatively little research on the effects of deet in humans.
"It has been used for many years, but there are recent studies now that show a potential toxicity," said Vincent Corbel, a researcher at the Institute for Development Research in Montpellier, France, and lead author of the study.
"What we have done is identify a neurological target for this compound," he said.
