BrainStuff Classics: How Dirty Is Soap?

brain Stuff? It's Christian Sager. It's good hygiene to wash your hands after using the restroom and after touching kind of gross stuff, you know, like raw meat, snakes, cat litter, cats, biomedical waist and any number of shared surfaces from door knobs to countertops. But what about soap? Bars of soap are also shared surfaces, So how dirty is soap? Soap is absolutely seething with bacteria, But you know, so is your face, and so so is my face and everything

we come into contact with all the every day. Really organism for organism, microbes outnumber humans on the planet at least a hundred and thirty one quintillion to one, Sell for sell. The microbes in and on our bodies outnumber us ten to one, and human hands can have up to one hundred thousand micro organisms per square centimeter of skin. Most of them are harmless or you know, even helpful, But yeah, there's a lot of them, and some of

them get transferred to your soap. One study from reported that of the bar soaps they tested, two to nine percent cultured positive for micro organisms. The antibacterial soap they tested actually had a bit more microbial activity than regular soap. The soaps in question we're in use by the staff of clinics and laboratories over the course of seven days,

and samples were taken on five of those days. But the interesting and come heating part of their results is that the microbes didn't build over the course of that week. Organisms would appear and disappear with each sample taken, indicating

one of two things. Either the soaps were somehow self sterilizing, possibly due to preservatives they contain that are you know, not delicious or downright dastardly to microbes, or the little buggers were being mechanically removed during the process of washing, meaning that as you wash your hands, you're also washing

your soap. These results back up a couple of other studies about microbes and hand washing, one from x and one from the former study had subjects come into their lab douse a hand in a vat of bacteria and then wash with a bar of soap. The soap was tested for the bacteria, then given to another subject to assess the transfer of the bacteria. The latter study carefully doused bars of soap with ec. Cole I and had subjects come in and first sterilize their hands, then wash

them with this gross soap. The researchers then tested both the hands and the soap from microbes. Both of these studies found that although bacteria remained on the soaps, none transferred to the participant's hands. Now here's the thing to note. These studies were done by employees of Procter and Gamble and Dial Corporation, respectively, and the first study I mentioned that one from that was completed with a grant from Minnatonka Incorporated, which was the original maker of soft soap.

That doesn't necessarily mean their science was bad, though experts say there's no evidence to contradict their results. So bar soap is not underty, but it's still safe to use and way better than not washing. So here's a few pro tips. Be sure to dry your hands thoroughly after washing, don't wash more often than necessary, that can lead to parched skin, which can crack, which can let in microbes. You otherwise would have been able to just wash off and make sure you store bar soap in a dish

that lets it drain and dry out between uses. That will cut down on any potential bacterial growth. Today's episode was written by me and produced by Tyler Clang. Brain Stuff is production of iHeart Radio's How Stuff Works. For more in this and lots of other clean topics, visit our home planet, how stuff Works dot com. Plus for more podcasts. For my heart Radio, visit the heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows,