Wait, should I bother using antibacterial soap?

A Vox reader asks: Why is some soap labeled antibiotic? Is there a soap that is friendly to germs, viruses, etc.? I thought the whole idea was to get rid of germs and viruses.

There really are too many varieties of soap out there. Too many brands, too many fragrances and colors, too many claims about their hand-softening, nail-beautifying, nostalgia-enhancing qualities to keep it all straight. And that’s before you even consider whether a product actually gets rid of disease-causing microbes. If this seems like too much, you’re not wrong; the market is overwhelming.

You may be surprised to learn that most “plain” soap doesn’t actually kill germs. Here’s what it actually does: When combined with water, it surrounds germs in slippery globs that make them literally slide off your hands and down the drain. Not lethal to microbes, but still a pretty efficient way to clean them off your hands.

Soap labeled as antimicrobial does more damage to microbes than just whisking them away — it does actually murder them by breaking up the outer layers of bacterial or viral cells and causing them to spill out their guts. These soaps contain additional ingredients that are particularly effective at slicing up the fatty compounds in germs’ outer walls, exposing the tiny organ-like structures on their insides and rendering them dead.

When it comes to getting rid of germs, it might seem that deadlier is better… right? Not necessarily. Antimicrobial soaps are indeed better at lowering the amount of germs on a person’s hands than plain soap — but in most situations, the risks aren’t worth that benefit.

One concern consumer safety experts at the Food and Drug Administration have had is that people who used certain antimicrobial soaps too often — specifically, soaps that contain any of nearly two dozen antiseptics historically used in consumer cleaning and handwashing products — might absorb some of those germ-killing ingredients into their bloodstreams. These chemicals tend to do the same thing to skin that they do to germs: break up the outer layers, causing damage and irritation.

The FDA was worried specifically about triclosan and triclocarban, the most widely used of these antiseptics. Animal studies suggested they could be absorbed from the skin into the blood, where they could go on to have hormone-like effects on the thyroid and on sex hormones. For other antiseptics, there was no good data proving they didn’t have these effects. The body of evidence raised questions about what might happen if a very zealous person took regular baths in a readily available antimicrobial soap.

The FDA also worried using antimicrobial soaps too frequently could create more microscopic superbugs that are harder to kill with common antibiotics. This isn’t just a theoretical concern: In one study, people who used a triclosan-containing antibacterial soap at home were more likely to have skin bacteria resistant both to the germ-killing ingredients in the soaps and to common oral antibiotics. Not great!

The risks of antimicrobial soap so dramatically outweighed their benefits that in 2016, the FDA banned most germ-killing ingredients from consumer products.

While they were conducting their review of antibiotic soaps, the FDA found that a handful of antimicrobials were actually safe enough to use at home: benzalkonium chloride, benzethonium chloride, and chloroxylenol. That doesn’t mean they have an advantage over plain soap in preventing infections — they don’t. It just gives manufacturers permission to market them to you. You can still find these in soaps labeled “antimicrobial” or “antibacterial” on store shelves today.

Manufacturers aren’t allowed to use those words to describe soap that doesn’t contain these ingredients, so most soaps don’t.

The key is in the killing, or lack thereof.

Germs often develop immunity by chance: They mutate pretty often as they reproduce, and occasionally, those mutations will give a handful of germ babies a survival advantage.

As an example, let’s say your bacteria-eliminating weapon of choice is a blowtorch. Given the frequency of bacterial mutation, five out of 100 bacteria living happily on a tiny section of your skin might have a mutation that makes them resistant to blowtorching. So if you try to clean that skin by blowtorching those bugs, you’ll end up with five living, blowtorch-resistant germs — each of which now has more space and resources to procreate and zero competition. Those elite germs will fill that space with their progeny, and the next time you want to clear that spot of bacteria, a blowtorch won’t cut it: Every member of this new, stronger bacterial population is already blowtorch-resistant.

Using a strategy that removes germs without killing them doesn’t create the same environment for those lucky mutants to thrive, so they stay small in number. That’s one of the major reasons why using plain soap is better for most situations than antimicrobial soap.

You didn’t ask about alcohol, but I’ll tell you this: Unless you have visibly dirty hands, or have norovirus or certain kinds of infectious diarrhea, alcohol-based sanitizers are a better choice than any soap.

They don’t get absorbed into the bloodstream through the skin. (Just don’t inhale them!) They also kill bacteria and many viruses more reliably than even antibacterial soaps, in large part because we apply them in the same concentration every time we use them. (Soap gets diluted by water, so it’s harder to be sure people are getting the same ratio of soap to skin.) That means superbug evolution isn’t a concern with these products.

Alcohol-based hand sanitizer is so much better than soap that the Centers for Disease Control and Prevention actually recommends sanitizer over antibacterial soap in most health care settings. One exception is before surgery: Because antibacterial soaps are still the best at removing bacteria from the skin just below the surface, surgeons still have to scrub with germ-killing soap and water before gloving and gowning up for surgery.