On the pro-chemical side are those who claim that plant-based sprays and other alternatives simply don't work at all, and so leave users exposed to pathogen-hosting insects carrying anything from West Nile to the bacteria that causes Lyme disease. But proponents of chemical-free repellents cite the possible toxicity of Deet to the human brain, and claim their all-natural alternatives work plenty well. (We'll add that we've had a pair of sunglasses get lightly melted by errant Deet spray, which left us questioning whether we ought to be applying it to our skin on a regular basis.)

The truth, as often is the case, falls somewhere in the middle. So according to Dr. Mustapha Debboun, editor of 'Prevention of Bug Bites, Stings and Disease,' both types of products have their place. "The way to think about it is that chemicals are better for longer hours in the deep woods," Debboun says, "while all-natural ingredients are fine for the backyard, beach, and other places where you won't be out for extended periods."