Most studies have focused on triclosan, and as far as human health is concerned the research into its toxic effects has produced mixed results. For nearly every study that shows triclosan has some particular effect, another shows it does not. Yet one thing is clear: Several clinical studies, following several hundred households, have shown that triclosan-based soap does not prevent illness any better than regular soap and water alone. ...[P]lain soap and water simply dislodge bacteria from skin, triclosan weakens and kills the microorganisms. Until recently it was thought that triclosan acted indiscriminately—killing all bacteria in a number of ways—but...