Poke around any bathroom or cleaning cabinet in the US and you’re likely to find a product spiked with an antimicrobial chemical. One of the most common of these, triclosan, has shown up in about 75 percent of antibacterial hand soaps and is easily spotted in a range of other goods, from toys to toothpaste. It has also been found in about 75 percent of Americans’ urine. Yet, despite their omnipresence, these antimicrobials go largely unregulated and scientists don’t know their health effects.

In an opinion piece published Thursday in Science, Alyson Yee and Jack Gilbert, microbiologists from the University of Chicago, call for that to change. They lay out just how little data we have on the chemicals—and some of it even conflicts. Yet, it’s clear that our exposure may begin in the womb and that the chemicals do have the potential to mess up our microbiomes—the communities of microbes in and on us that strongly influence our health. Such microbial disturbances have been linked to wide ranging conditions, from neurological disorders to arthritis, allergies, obesity, and irritable bowel disorder.

As such, scientists should prioritize figuring out if the chemicals that are already all around us, are causing harm, Yee and Gilbert argue.

To make their case, the pair first lay out how easy it is to come into contact with antimicrobials: they’re in wipes, toothpaste, cosmetics, cutting boards, detergents, toys, plastics, as well as hand soaps. And they readily sink into skin if they don’t make their way into a mouth via a toothbrush or a contaminated hand. Studies have found evidence of exposure in utero and around birth, particularly in hospitals, which heavily rely on antimicrobials to curb the spread of germs to vulnerable patients. Exposure so early, while the microbiome is still getting established, may have lasting but subtle impacts on health, the authors note.

As Ars has written about before, triclosan and its ilk have the ability to spur the development of drug resistance and help out drug-resistant microbes. But Yee and Gilbert focus mostly on the potentially stealthier harm, the injury to the microbiome. Studies using zebrafish (which can be used as a model organism for vertebrate development) and flathead minnows both found that triclosan alters gut microbiomes. Those studies also suggested that the gut microbiomes can rebound after triclosan is removed. However, a study of microbes in waterways found that triclosan exposure made permanent changes to communities.

In a study from earlier this year, Stanford and Cornell researchers tried to look at such effects in people. They split 13 volunteers into two groups—one group used triclosan-containing products for four months, then switched to non-triclosan containing products for another four months. The other group did the reverse. At the end, the researchers didn’t find any statistically significant differences or changes in their gut or mouth microbiomes. Yet, the researchers didn’t test for antimicrobials other than triclosan. And the volunteers still had triclosan in their urine when they weren’t purposefully using triclosan-containing products.

“It is also possible that triclosan exposure is so ubiquitous, starting as early as prenatal exposure, that the human microbiota has already adapted,” Gilbert and Yee point out. Researchers need to do far more research, the pair conclude.

In the meantime, some regulators have already begun to worry about the problem. The European Union and the state of Minnesota have passed partial bans on the chemicals in commercial products. The US Food and Drug Administration is currently reviewing data on the safety and benefits of triclosan in hand soaps. However, one data point that does seem clear in this issue: studies have clearly found that under normal hand washing conditions antibacterial hand soaps are no better at ridding grimy hands of bacteria than regular soap and water.

Science, 2016. DOI: 10.1126/science.aag2698 (About DOIs).