How clean should your skin be?

Soaps that strip away microbes aren't good, but it may be too soon to try products that add bacteria back.

You may have noticed that antimicrobial skin cleansers have disappeared from the shelves. In September 2016, the FDA ruled that over-the-counter antiseptic soaps and wash products containing triclosan, triclocarban, or 17 other antimicrobial agents could no longer be marketed because their manufacturers didn't demonstrate that the ingredients were both safe and effective in preventing the spread of infections. Moreover, the widespread use of antimicrobials is thought to promote the growth of antibiotic-resistant bacteria, like methicillin-resistant Staphylococcus aureus (MRSA), which can cause infections that are difficult to treat and even life-threatening.

You may also have noticed some new sprays, creams, and lotions whose purpose is just the opposite. Rather than eradicating microbes from our skin, these products, called probiotics, are designed to aid the growth of certain beneficial skin bacteria.

In theory, probiotic skin products make sense, says Dr. Suzanne Olbricht, chief of dermatology at Harvard-affiliated Beth Israel Deaconess Medical Center. She cites a growing body of research showing how our commensal microbes — the native populations of bacteria, viruses, and fungi that colonize our skin — enhance our health. "It's time to stop thinking 'us versus our bacteria' and begin thinking 'us plus our bacteria,'" she says.

Why probiotics have potential

Just as physicians are using fecal bacteria from healthy people to treat intestinal disorders, so might dermatologists use skin bacteria from people with healthy skin to treat chronic skin conditions. In such cases, beneficial strains of bacteria multiply faster and leave less room for disease-causing strains. There are a few small studies indicating that probiotics may be useful in treating dry and sensitive skin as well as acne.

Should you try them?

Although probiotic skin products are already available online and in stores, many questions remain. Does any product have the right mix of bacteria to treat a specific condition? Is it safe? Is it effective? Manufacturers need to conduct randomized controlled clinical trials to provide the answers. None have done so to date.

"We're just at the cusp of understanding this. Someday — maybe in five or 10 years — we can wash our hands and apply some good bacteria to protect our skin," Dr. Olbricht says. For now, for most people with normal skin, plain old soap is still the best option.

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