Antibacterial soaps containing triclosan were designed to protect hospital patients vulnerable to infection, not to be slathered on like Old Spice on prom night. Also found in shampoos and certain toothpastes, triclosan is an endocrine disrupting chemical (EDC)—it messes with your hormones—that has been shown to interfere with reproductive systems in some freshwater fish. Specifically, it boosts levels of female hormones in male fish and decreases their sperm count. Fish are literally swimming in triclosan, which gets flushed down our drains and makes its way into streams. We, on the other hand, have a choice about whether to use such products. Though it hasn't been proved that triclosan impacts human fertility, ask yourself this: Do you want to volunteer for that study?
Source: "Triclosan Has Endocrine-disrupting Effects in Male Western Mosquitofish," Environmental Toxicology and Chemistry