Triclosan

Triclosan may be used in a number of consumer applications as an antibacterial and antifungal agent. It has historically been present in soaps and detergents, toothpaste, toys, and surgical cleaning products, though it is gradually being eliminated from many commercial and cosmetic products. Because of its possible contribution to antimicrobial resistance and the risk that it is an endocrine disruptor, its use is controversial. Triclosan was first developed in 1964 and was commonly used as a hospital scrub when first available. As it expanded, it became a common ingredient in multiple commercial products, including socks, bedding, and trash bags. By the turn of the 21st century triclosan was found in the majority of liquid soaps, several types of bar soap, and in more than 2,000 other consumer products; as of 2019, however, it was removed from cosmetic and hygienic products by multiple large corporations.

In clinical settings, triclosan is an effective regimen for decolonizing patients with MRSA and has been shown to correlate with the reduction of MRSA infections. Surgical sutures that are coated with triclosan have been shown to reduce the risk of infection at surgical sites, a claim that is supported by the World Health Organization, the American College of Surgeons, and the Surgical Infection Society.

In commercial applications, triclosan’s use is more contested. While antimicrobial hand soaps that contain triclosan are likely to reduce bacteria on the hands, the benefits are slight, and the FDA has stated that there is no evidence that triclosan in soaps and body washes provides a greater benefit than simple soap and water. Toothpaste containing triclosan has been determined to provide a 22% reduction in inflammation of the gum tissue and in dental plaque when compared to toothpastes without triclosan, but there is insufficient evidence that this led to fewer cavities or a reduction in periodontitis.

Triclosan has been determined to be a “contaminant of emerging concern” and was listed as an ingredient that is not recognized as safe and effective in 2016, after being investigated as a public health risk due to its possible contribution to antimicrobial resistance and endocrine disruption.
Triclosan is believed to accumulate in wastewater and has been found in drinking water, possibly contributing to a buildup that could increase adverse effects as it accumulates. In chlorinated tap water, triclosan may also react and convert to dioxins. Triclosan has also been connected with a higher risk of food allergy, as well as inhalant and seasonal allergens, and it may also cause allergic contact dermatitis. This may be due to the reduction of bacteria -- the hygiene hypothesis -- or it may be due to the toxicology of triclosan.

Triclosan was first suspected as a possible endocrine disruptor when it was detected in breast milk and blood and urine samples from humans. In laboratory settings, triclosan exposure has been shown to possess antiestrogenic and antiandrogenic properties. In a 2017 Chinese study on pregnant women, triclosan exposure during pregnancy was connected to increase testosterone levels in the infants.
Because triclosan effectively kills a wide array of bacteria, it also has an adverse effect on the beneficial bacteria found in soil. It is toxic to bacteria in aquatic systems and is highly toxic to algae. Residual triclosan has been found in many types of aquatic organisms and is also found in land animals. While there is not enough long-term data to determine its toxicity over time, it has been demonstrated to have acute toxicity in these organisms. Triclosan is more common in soil and sediment because it prefers anaerobic conditions and is resistant to anaerobic degradation. It may also cause cross-resistance to other antimicrobials in humans; for example, after being exposed to triclosan, two common bacteria types demonstrated increased resistance to other, unrelated antibiotic families.