Insect repellents: which keep bugs at bay?(up front: News/ Trends/ Advice)

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. We also tested Buzz Off Flick Tee, a permethrin-treated cotton shirt, which claims to repel insects for 25 washings.

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. The best nondeet product was Repel Plant Based Lemon Eucalyptus, but volunteers criticized its odor. In tests last year, Cutter Advanced with 7 percent picaridin repelled mosquitoes well, but this time we found less protection.

In lab tests, the Buzz Off Flick Tee didn't work well. Within 2 minutes, aedes mosquitoes had bitten the lab director at least 35 times through material washed once. Some research suggests that permethrin-treated fabric might work better outdoors, but even a treated T-shirt won't protect bare arms.

CR's take. Products containing at least 30 percent deet worked very well; most of the botanicals we tested were middling or worse.

 
Quick Ratings Insect repellents 
 
In performance order. 
 
Product                    Active          Type      Cost/ 
                           ingredient                oz. 
 
Off Deep Woods 
For Sportsmen I            deet 98%        pump      6.5 cents 
 
3M Ultrathon               deet 34%        cream     3.8 
 
Off Deep Woods 
For Sportsmen IV           deet 30%        aerosol   0.7 
 
Cutter Unscented 
Outdoorsman                deet 30%        aerosol   0.8 
 
Ben's Wilderness 
Formula                    deet 30%        pump      3.2 
 
Repel Sportsman Formula    deet 20%        cream     2.0 
 
Repel Sun & Bug Stuff      deet 20%        cream     1.3 
                           (+ sunscreen) 
 
Repel Plant Based Lemon    p-menthane-3, 
Eucalyptus                 8-diol, 26%     pump      1.9 
 
Cutter Advanced Sport      picaridin 15%   aerosol   0.9 
 
Off Skintastic IV         ...