The Case Against Antibacterial Soap Is Getting Stronger

If you wash your hands in public restrooms, brush your teeth and wear antiperspirant, you’ve come in contact with triclosan, an antibacterial used in many personal care products. But mounting evidence, much but not all of it done on animals, has linked triclosan to bacteria resistance, hormone disruption, and possibly even liver cancer. These studies were published after the Food and Drug Administration, which regulates personal care products, deemed it generally recognized as safe (GRAS), but in light of the new evidence, the agency is currently reviewing the new research.

Now a new study done in zebrafish suggests triclosan also messes with our gut—interfering with the community of bacteria that makes up our microbiome. In the new study, published Wednesday in the journal PLOS ONE, researchers at Oregon State University exposed 45 adult zebrafish to either normal food or food with triclosan for up to seven days. After that, the researchers analyzed the microbiomes of the fish and found that exposure was linked to significant shifts in the diversity and structure of the fish’s microbiome.

“Consider the diversity of chemicals we consume on a daily basis, any of which could have an unpredictable impact on the gut microbiome,” says study author Thomas Sharpton, an assistant professor of microbiology and statistics in the OSU Colleges of Science and Agricultural Sciences. “By using zebrafish, which is inexpensive to grow in high volume and grows rapidly, we can relatively easily screen for those chemicals that disrupt the microbiome.” Sharpton says the chemicals or ingredients that cause a change in the microbiome in fish can then be followed-up for effects in mice or humans.

Zebrafish are not humans, of course, but Sharpton says zebrafish are widely used to study environmental chemical exposures, and that his findings merit further research into the effects of triclosan on the human microbiome.

While the levels of triclosan in products are usually deemed too low to cause the most severe forms of disease linked to the ingredient, the study authors note that research is increasingly connecting the microbiome to health, and that disruption of the body’s bacterial make-up could contribute to a variety of diseases.

Another September 2015 study published in the Journal of Antimicrobial Chemotherapy found that the antibacterial cleansing formulas do not kill more bacteria than soap and water, which is a good option for people who want to prevent exposure.

The study did not determine whether changes in the microbiome observed in the study causes disease, but Sharpton says his team is looking at the effects of varying levels of triclosan on the gut microbiome to attempt to answer that question.