If the label on your hand soap proudly boasts that it kills 99 percent of germs, it might be time to stop using it. According to a consensus statement signed by over 200 scientists and medical professionals, there's no evidence that so-called antimicrobial chemicals actually do anything to prevent illness – and worse, they might be actively harming your health and the environment.

First presented at the DIOXIN International Symposium in 2016, the Florence Statement gathered current research on two specific antimicrobial chemicals, triclosan and triclocarban, which have been widely used for decades. The document pointed out that there's insufficient evidence that these chemicals are safe to use or are even effective in the first place.

"People think antimicrobial hand soaps offer better protection against illness," says Barbara Sattler, an environmental health professor at the University of San Francisco. "But generally, antimicrobial soaps perform no better than plain soap and water."

In response, the US Food and Drug Administration (FDA) banned the use of triclosan and triclocarban, as well as 17 other microbial ingredients, in over-the-counter products like soaps.

"I was happy that the FDA finally acted to remove these chemicals from soaps," says Arlene Blum, PhD, Executive Director of Green Science Policy Institute. "But I was dismayed to discover at my local drugstore that most products now contain substitutes that may be worse."

This could just lead to an arms race, as companies keep substituting banned additives with new ones that could be just as harmful. And the antimicrobial ban doesn't stop them being used in other personal care, building and consumer products, like toothpaste, paints, food storage containers, clothing, kitchenware and flooring.

"Added antimicrobials are marketed as beneficial in building products from countertops to doorknobs and light switches," says Bill Walsh, President of Healthy Building Network. "Antimicrobial preservatives are useful in certain products like paints, but we found claims about health benefits to be largely invalid."

Besides the obvious issue of the additives not doing what they're supposed to do, the Florence Statement cites studies suggesting that exposure to triclosan can make people more sensitive to food allergies and asthma, and negatively affect human reproduction and development. Increased use of antimicrobial products means we're not only exposing ourselves to these chemicals, but more of them are washing into the environment and affecting animals and ecosystems in similar ways.

Worse still, if they are effective at killing microbes, the chemicals could be contributing to the rise of the superbug, as bacteria continuously evolve stronger defences against our best antibiotics.

To counter all that, the Florence Statement recommends a few new rules. Triclosan, triclocarban and other antimicrobials should be avoided unless there's enough evidence that they're safe and beneficial, and safer alternatives should be considered instead. Before an antimicrobial is allowed to be used in a product, its long-term health and environmental impacts should be studied, and all products containing these chemicals should be clearly labeled.

The Florence Statement was published in the journal Environmental Health Perspectives.