Triclosan can irritate skin, disrupt thyroid and immune system function, and cause allergies, eczema and asthma, according to Beyond Pesticides. As of 2015, the FDA claims triclosan is not known to be harmful to humans, but it is investigating further in light of studies showing adverse hormonal effects on animals.
Triclosan is an antibacterial compound found in many products, including toys, kitchenware, clothing, toothpaste and antibacterial soaps. Although triclosan has been shown to prevent gingivitis, it has no proven benefit in other household chemicals humans frequently use, according to the FDA. Soaps containing triclosan do not clean better than those without the chemical.
Triclosan builds up in the body. Studies have found traces of the chemical in about 75 percent of people in the United States. Animal studies show that the chemical causes problems with hormones affecting development, metabolism and reproduction. Triclosan leeches into the environment from human use and can affect aquatic ecosystems and animals.
Triclosan has also been linked to promoting antibiotic resistant bacteria, which can cause severe infections in humans. The CDC considers antibiotic resistance to be one of the most important issues plaguing the United States, according to the Natural Resources Defense Council.
Products containing triclosan must include it in the list of ingredients or in the drug facts section on the label, according to the FDA.