Insect repellents
Which keep bugs at bay?
Bzzzzzzzz ... swat! If those words made you wince, read on for results of our tests showing how well 18 repellents ward off
mosquitoes and ticks. Some kept the little beasts away for at least 12 hours; others barely worked.
How we tested. A lab enlisted four victims--er, volunteers--who thrust treated arms into separate cages, each home to about 200 aedes mosquitoes,
an aggressive species that can carry dengue fever, or about 200 culex mosquitoes, a calmer species that can carry West Nile
virus. (Ours were uninfected.) Arms were exposed for five minutes at regular intervals. The effectiveness period was deemed
over when a volunteer was bitten twice in a session or once in two consecutive sessions.
For tick tests, we placed about 12 uninfected, hungry deer ticks, the type that can transmit Lyme disease, on little test
plates strapped to each of a volunteer's arms. A hole in each plate exposed a patch of skin, and our score was based on the
number of times ticks walked over treated skin.
What we found. Hours of protection correlated with deet concentration. The top-rated Deep Woods Off is 98 percent deet, and several products
with 30 to 34 percent deet were very good, protecting for an average of at least five hours. The U.S. Environmental Protection
Agency has found deet safe when used according to directions (not under clothing, in an open cut, or with sunscreen), but
some people dislike its scent or feel. Use the lowest concentration that works, especially on kids, and don't use deet on
infants.
CR's take. Products containing at least 30 percent deet worked very well; most of the botanicals we tested were middling or worse.
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