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Science in the News

Human Crossover Control Study of Triclosan's Impact on the Microbiome

May 19, 2016

A 2013 Cochrane review concluded that fluoride toothpaste containing triclosan reduced plaque and gingivitis more than toothpaste containing fluoride alone.1 A study by Poole et al. in the May 2016 issue of mSphere,2 a publication of the American Society of Microbiology, was designed to examine whether use of consumer products (e.g., toothpaste, liquid hand soap, solid hand soap, and dishwashing liquid) would alter gut microbiome composition, endocrine function, and markers for obesity, diabetes, and inflammation. This was a double-blind, randomized, crossover study in which participants (n=16 enrolled) were given either triclosan/triclocarban-containing (TCS) or non-triclosan/triclocarban-containing (nTCS) products that they used for 4 months, at which point they were switched to use of the other set of products for 4 months. Investigators collected blood, stool, gingival plaque, and urine samples at baseline and throughout the study period. In addition, they monitored the body weight of study participants.

Urinary triclosan levels were higher (p<0.001) in the TCS phase than in the nTCS phase of the study. No significant differences were observed for the TCS phase as compared with the nTCS phase in levels of testosterone, T4, thyroid-stimulating hormone, or in any of the 25 obesity and diabetes markers measured. Approximately half of the study participants gained more than 0.6% of their body weight in the TCS phase, but lost or maintained their weight in the nTCS phase. In terms of the microbiome, although there appeared to be significant decreases of several taxa, including those associated with periodontal disease, none of the associations were significant after correction for the false-discovery-rate. There were no significant differences in microbiome species diversity observed.

The data in this study2 do not provide insight about mechanism of the effects observed in the 2013 Cochrane review.1 However, notwithstanding significant differences in excreted levels of triclosan, the results of this study are not consistent with the hypotheses that use of triclosan at physiologic levels achieved through the use of consumer products has a major impact on human gut or oral microbiome composition, or the metabolic and inflammatory markers measured in this study. This study does not address questions related to environmental impact of triclosan, but is strongly suggestive of its safety for use by humans.


  1. Riley P, Lamont T. Triclosan/copolymer containing toothpastes for oral health. Cochrane Database Syst Rev 2013;12:CD010514.
  2. Poole AC, Pischel L, Ley C, et al. Crossover Control Study of the Effect of Personal Care Products Containing Triclosan on the Microbiome. mSphere 2016;1(3):e00056-15.

Prepared by: Center for Scientific Information, ADA Science Institute

About Science in the News

Science in the News is a service by the American Dental Association (ADA) to its members to present current information about science topics in the news. The ADA is a professional association of dentists committed to the public's oral health, ethics, science and professional advancement; leading a unified profession through initiatives in advocacy, education, research and the development of standards. As a science-based organization, the ADA's evaluation of the scientific evidence may change as more information becomes available. Your thoughts would be greatly appreciated.

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