Nothing is as effective as DEET at warding off bugs, and decades of research by the EPA and CDC have backed up its safety. This spray kept us bite-free all day lakeside at Quebec’s Gatineau Park with a single application (though it will sweat off), repelling clouds of black flies and mosquitos. DEET will break down plastics, so take care what you put it on. We also tested the 30-percent DEET formula and found it nearly as effective, but not as long-lasting. (Upside: The weaker formula dries skin out less.) $10; 3.4 oz.