Repellant works, but fears linger
Like many conscientious parents, Dr. Robert Nevin makes sure his children are protected by insect repellent when they’re outside. But instead of spraying the more common brands, he slathers on a preparation made with soybean oil.
This alternative, Nevin says, keeps his children safe from both mosquitoes and DEET, the chemical in most commercial insect repellents.
Now found in sunscreens, wipes and a variety of sprays and sticks, DEET is recommended by the Centers for Disease Control and Prevention as a way to prevent bites from mosquitoes that may be carrying the West Nile virus. Both the Environmental Protection Agency and the CDC have concluded that the chemical (N,N-diethyl-m-toluamide) is not toxic for humans when used as directed.
“All the studies say that this is still safe to use,” said Laurene Mascola, chief of the Acute Communicable Disease Control Program in Los Angeles County. But some parents -- and health experts -- have their doubts about the chemical. Many rely on the increasingly available alternative preparations, made from natural products.
The U.S. Army developed DEET in 1946 to ward off ticks and mosquitoes for its soldiers, and the chemical became available to the public in 1957. Studies have found DEET to be the longest-lasting mosquito repellent on the market.
But the chemical is also capable of dissolving watch crystals and eyeglass frames, and the Environmental Protection Agency has linked it to a few seizures and deaths over the years.
“We don’t know that these are safe for our children neurologically,” said Nevin, a family doctor in Toronto. Even public health officials who recommend DEET use say that dousing yourself frequently with the chemical is probably not smart. The American Academy of Pediatrics recommends limiting application to once a day for children.
Since 1960, between 14 and 46 cases of seizures have been associated with DEET contact, sometimes by children ingesting the chemical. Between 50 million and 80 million Americans use DEET every year.
Studies at Duke University Medical Center in 2001 indicated that long-term use of DEET, in combination with other chemicals, killed neurons in rats’ brains.
The CDC and EPA recommend taking precautions when using DEET repellents. For instance, the chemical shouldn’t be sprayed on open wounds, should be washed off as soon as possible and shouldn’t be applied to children’s hands (which can find their way into kids’ mouths).
Nor should parents use DEET on children younger than 2 months. “When it comes to infants, we don’t really know much,” said Mohamed Abou-Donia, professor of pharmacology and cancer biology at Duke who led several DEET studies. But Mascola says children are at a relatively low risk of being infected with West Nile virus. The median age of the 57 people diagnosed nationwide with West Nile this year, through June 29, is 53. Ten of those cases have been in California. Consumers who want protection against mosquitoes but would prefer a natural alternative should know that those repellents may need to be applied more frequently.
A 2002 study in the New England Journal of Medicine found that natural insect repellents did not last as long as DEET. Soy bean oil-based repellents, for example, protected against mosquitoes for an average of 94 minutes. Other botanicals, including citronella, lasted less than 20 minutes. A repellent with 23.8% DEET, such as Deep Woods Off, would keep mosquitoes at bay for an average of five hours.
Higher concentrations of DEET generally mean longer protection from mosquitoes, but for children, the American Academy of Pediatrics recommends applying repellent containing less than 30% DEET. “More is not necessarily better when it comes to DEET,” said Daniel Sudakin, an assistant professor of toxicology at Oregon State University. “I think that based on the available scientific data, insect repellents containing DEET are safe and effective when used according to labeling instructions,” he said.
