Somewhere along the way, a lot of people decided that bar soap was a little bit gross. A slab of something everyone in the house rubs on themselves, sitting in the shower collecting who knows what. It's an understandable reaction, and it's also mostly wrong.
Yes, bar soap is sanitary. Bacteria can live on the surface of a used bar, the same as on nearly everything else in your bathroom, but the research has been consistent for decades that washing with a used bar doesn't pass those bacteria on to your hands. Here's why, and how to keep a bar in good shape.
How soap actually cleans
Soap molecules have two ends. One end is drawn to water, and the other is drawn to oil and grease. When you lather up, the oily end grabs onto the oils on your skin, along with the dirt and germs stuck in them, and the watery end lets the rinse carry the whole lot down the drain. It's less about killing anything and more about lifting it off and sending it away.
That's also why the scrubbing matters so much. The rubbing and the running water do the real work, and the soap makes it possible. If you want the longer version, we wrote about how soap works.
What the research says
Scientists have been poking at this question since at least the 1960s. A 1965 study concluded that bacteria weren't transferred from person to person by a shared bar, and that the soap didn't support bacterial growth.
The study people quote most is from 1988. Researchers deliberately loaded bars with E. coli and Pseudomonas aeruginosa, at about 70 times the levels typically found on used soap, and had 16 people wash their hands with them as usual. Afterward, none of the 16 had detectable levels of either bacterium on their hands.
So the bar can carry bacteria, but the bacteria don't seem to make the trip.
So why do people think it's dirty?
Partly instinct. A wet, slightly gooey bar doesn't look clean, and the gunk in the bottom of a soggy dish is genuinely unappealing. But it's hard to ignore that the worry about bar soap grew right alongside liquid soap in the 1980s, when there was a new, pricier product to sell and a reason to make the old one seem a bit suspect.
Liquid soap is perfectly good soap. It just isn't any cleaner. And it comes in a plastic bottle, which is part of why a 2009 life-cycle study out of ETH Zurich found liquid soap took considerably more energy to produce and package than bar soap.
How to keep a bar of soap clean
"Clean" is doing a lot of work in that heading, but you get the idea.
- Let it dry. A dish that drains, out of the shower spray, is the most important thing you can do. A bar that stays wet stays slimy, and slime is where the ick lives.
- Give it a rinse. A quick rinse of the bar before you put it down washes off the lather and anything in it.
- Clean the dish. The dish is usually grosser than the soap. Rinse it out every week or so.
- Keep your own if you'd like. The research says sharing is fine. If it still bothers you, a bar per person costs very little and settles the matter.
A dry bar also lasts a lot longer, which we get into in how long a bar of soap lasts.
Is castile soap sanitary?
Yes. Castile soap is soap, and it cleans the same way any soap does. The only thing to watch is that pure olive oil soap goes soft faster when it's left wet, so the draining dish matters even more. Our castile bars are made with 100% organic olive oil, plain or with essential oils like eucalyptus, tea tree and peppermint.
Bar or liquid, then?
Whichever you'll actually use. Both lower the number of germs on your hands when you wash properly, which means at least twenty seconds of scrubbing and a good rinse under running water. Technique beats format every time.
We make bars, so you know which way we lean. If you're ready to give one a try, the whole soap shelf is right here.