Triclosan is a chemical compound that was first developed for soaps used in surgical scrubbing due to its antibacterial and antifungal properties. It has since expanded commercially and is commonly found in consumer products where these properties are desirable, such as toothpaste, soap, detergent, mouthwash, general cleaning products, and toys. It's also commonly used in compounds used to clean surgical instruments.
Although it's clearly effective in the appropriate products, testing by the FDA shows that some products, such as antibacterial soaps, are no more effective with triclosan than without it.
Triclosan is seen as harmless to humans in the amounts they would typically be exposed to, but it's also recognized that accumulations of large amounts can be harmful to the environment as the amount remaining even after sewage treatment can disrupt the growth of algae. It can also accumulate in the fat of sea creatures.