Keeping mosquitoes away is a matter of comfort. Nothing wrong with that. But in recent years, American public health officials have started taking repellents seriously as a matter of disease prevention because of mosquito-borne West Nile virus. The only ingredient that has gotten the government's full-fledged endorsement has been the chemical DEET.
But DEET lost its monopoly in spring 2005 when the Centers for Disease Control and Prevention said that research has shown that two other repellent ingredients, picaridin and oil of lemon eucalyptus, are also effective.
Picaridin, a derivative of piperidine, a chemical related to black pepper, has been used in Europe since the late 1990s. In this country, Cutter Advanced was the first picaridin product to hit the market. Oil of lemon eucalyptus, also known as p-menthane-3,8-diol, has also been used as a repellent elsewhere. The repellents in the United States that contain it include Repel Lemon Eucalyptus and Off! Botanicals.
DEET, which has a long track record, is safe but many people worry that it's not. Apart from safety concerns, many find the chemical feel and smell of DEET-based products unpleasant. So-called natural alternatives have been around for years, but tests — and mosquito-bitten buyers — have shown that they aren't all that effective.
The big advantage of DEET is that it lasts — and you don't have to use the super-high-concentration products. We won't count on this in a real, mosquito-infested situation, but in controlled lab conditions, a repellent containing 20% DEET (an average amount) keeps mosquitoes from biting for four hours.
Dr. Mark Fradin, a dermatologist in Chapel Hill, North Carolina, who has researched insect repellents, says products containing picaridin and oil of lemon eucalyptus should last about four hours, so their staying power is similar to many of the DEET-based repellents. That's good news for people who have wanted an alternative to DEET and, we hope, bad news for this summer's swarms of blood-thirsty mosquitoes.