Latest Results on Insect Repellents

Many divers avoid some tropical venues because of biting bugs like mosquitoes and no-see-ums. Here’s help.

Consumer Reports (June 2006) used human subjects who tested 18 repellents by thrusting their arms into cages with 200 aedes mosquitoes, an aggressive species that can carry dengue fever, or 200 culex mosquitoes, a calmer species that can carry West Nile virus. Both can be found on every continent but Antarctica.

Generally, the higher concentration of the chemical DEET, the more effective the repellent. The toprated Deep Woods Off is 98 percent DEET, and kept the aedes away for 12 hours and the culex at bay for 13. Several products with 30 to 34 percent DEET protected for at least five hours. Products with seven percent DEET lasted only an hour against the aedes.

While the U.S. Environmental Protection Agency has found DEET safe when used according to directions, many divers use non DEET products such as Repel Plant-Based Lemon Eucalyptus. It finished behind the products with 20 percent DEET, but offered nearly four hours of protection. Herbals like Bite Blocker and Natrapel offered little if any protection against the aedes mosquito, though some against the culex. A favorite with divers, Skin-So-Soft, offered no protection at all against the aedes mosquito. In tests last year, Cutter Advanced with 7 percent picaridin repelled mosquitoes well, but this time they found less protection. Most botanicals tested were middling or worse.