Bar soaps have a bad reputation. Manufacturers of liquids, creams, and foam formulations have led us to believe that soaps strip away healthy oils, cause our skin cells to fall off in invisible flakes, and—even worse—are simply cesspools of bacteria left behind by previous users.
It’s true: Germs do live on bars of soap. Several studies over the past decades have shown that bar soaps used at home and in public places harbor bacteria, such as E. coli, Staph. aureus, and Staph. epidermidis. The more heavily used a bar is, the more microorganisms it holds. But does that really mean it's time to leave bar soaps behind?
Can a bar of soap make me sick?
First, it’s very unlikely that the microbes found on bar soap will make you sick. “There’s not a lot of evidence that bacteria from bar soap is transferred to the next person,” says Marlene Wolfe, an environmental health researcher at Tufts University who studies the role of handwashing in the removal of infectious pathogens.
Studies going as far back as 1965 show that even when scientists intentionally contaminate their hands with disease-causing E. coli and Staph, and bacteria are transferred to the surface of a bar of soap, those microorganisms aren’t detected on the skin of a second person who lathers up with the same slimy bar.
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Another study in 1988 confirmed these findings. This time, scientists funded by Dial contaminated soap bars with 70 times the amount of bacteria that normally live on used soap. They asked sixteen people to wash their hands with the soap, and couldn’t find traces of the contamination on any of their hands. In fact, Wolfe’s work, published in the journal PLoS One last year, suggests that good old bar soap is pretty effective at removing viruses from people’s hands too.
“One of the drawbacks of a lot of handwashing research that’s been done is that it is based on bacteria,” she says, “And more and more of the diseases that we’re concerned about globally are caused by viruses.”
Are bar soaps as effective as hand sanitizers for removing viruses and bacteria?
To test how well seven different handwashing techniques worked, Wolfe and her team recruited 18 volunteers and inoculated their hands with either E. coli or a virus that would mimic Ebola. They found that one minute of rigorous handwashing with bar soap was as good as a dollop of hand sanitizer and or a chlorine rinse that some doctors use—for removing both bacteria and viruses.
“Bar soap is good at mechanically removing germs that are transiently on your hands,” says Elaine Larson, associate dean for research and professor of epidemiology at Columbia University’s School of Nursing. The gunk we want to wash off our hands, whether it’s dirt or germs, clings to us because of the natural oils on our skin.
Soap molecules are designed to break up that oil into smaller drops, loosening up any sticky microbes in the process. The other end of the soap molecule remains “hydrophilic,” or water loving. When you turn on the faucet, the soap takes those now loose flecks of dust and germs down the drain. Whee!
What's the most effective way to wash my hands with bar soap?
Basically, all you need to do is make sure you wash your hands well. Spend 20 to 30 seconds scrubbing each side, make sure to scrape under your nails, and wash up to your wrists. You don’t need any additional antibacterial substances, like triclosan, in your soap, Larson says. They actually breed more aggressive bacteria, and are best avoided.
“As long as you make sure it hasn’t been sitting in sludge, using regular bar soap works perfectly well,” she says. “And if it has been sitting in sludge, just rinse it off with running water before you use it.”
It’s the nasty puddle that bar soap often sits in that allows germs to thrive in the first place. That’s why wet towels, loofahs, and kitchen sponges are also havens for microorganisms. But storing soap in a dish with ridges to keep it out of water and allowing it to dry between uses will go a long way toward limiting the number of germs you’re exposed to.
One scenario where you might want to be extra cautious: If your roommate, partner, or family member is sick with the flu, diarrhea, or some other infectious bug. In that case, maybe consider switching to liquid soap. That’s why hospitals and public restrooms also generally have liquid soap dispensers: They limit germ exposure even further.
The bottom line, however, is that if you’re healthy, you shouldn’t worry about catching bugs by sharing your soap. “The problem with bar soap is mainly aesthetic,” Larson says.
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