Can a soap be dirty? In a sense that there are still some bacteria living on it.
In: Chemistry
Yes it can be. Bacteria love to grow in damp, dark, warm places such as underneath a bar of soap in the bathroom. It’s also worth noting that every person in your household should be using their own bar of soap due to the risk of transferring bacterial between members. I’ve had patients who gave their SO a staph infection from sharing soap. Also had one that kept getting recurrent bacterial infection in his face because of bar soap. Using liquid body wash is much more hygienic. If you must use bar soap, put it in a place where both sides can dry. If you use a body scrub/loofah make sure those dry thoroughly as well.
Soap is an EXCELLENT source of food for bacteria, especially when coupled with water. As others have said, it’s the surfactant properties of soap that clean you, it is in no way antibacterial. You should see some of the stuff that grows from cultures of soap that isn’t made in a super sanitary way.
Source: I work for a large soap manufacturer.
Yes, it is advised that immunocompromised individuals should avoid bar soap and cloth hand towels and instead should use liquid soap and paper towels
Definitely. Soap removes bacteria mechanically, meaning they make the bacteria slippery, causing it to flow away when you rinse. Therefore, bacteria won’t die on the soap. They can only slide around.
A lot of misinformation here.
First of all, domestic-use anti-microbial soap is notoriously bad at removing bacteria. Some studies show zero benefit over normal soap.
Secondly, of course soap and other detergents disrupt cell membranes, including that of most bacteria. Even your hands will eventually suffer after the layer of dead skin has been removed due to repeatedly washing.
However, the process is not fast, some bacteria might be more resilient, viruses might be completely unaffected, as well as some more exotic bacteria that go into a dormant state where even antibiotics or desiccation will not harm them. They would still be able to sit on a completely dried out bar of soap, waiting to reproduce when conditions improve.
So the answer is: some bacteria and some viruses might be able to live on a bar soap or inside a container of liquid soap, so yes, it might be dirty in the sense of not being sterile.
One of the reasons why surgeons scrub their hands so extensively with soap containing harsh antimicrobial agents, usually chlorhexidine or povidone-iodine, which cannot be found in antimicrobial soap for domestic use. It usually only contains triclosan in low concentrations, which on paper is a good antimicrobial agent, but in practice and in soap doesn’t make much of a difference.
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Not eli5, since I don’t know how to really get it to that level. There are only a couple ways to mostly clean something. One is in an autoclave, which uses pressure and steam mostly to kill almost everything (only a few types of spores survive and it’s exceedingly rare). Bleach and alcohol also work, but those require certain concentrations and/or time frames to really work. Basically, soap isn’t all that good, since it usually only breaks up water surface tension so that the water gets “wetter” and can reach more places. The act of scrubbing your hands together does most of the work.
Now your skin is mostly bacteria. So when you’re using soap (especially bar soap), a lot of that bacteria – both from your skin and the bacteria on your skin from the environment – are pulled off, which is the point. That bacteria can live in the soap for quite some time, feeding on both other bacteria or other things that come out of the air. When things get too rough, they can enter a hibernation-like state or form spores to wait until conditions are better.
Anti-microbial soaps do more than break surface tension of water and have extra things to actively kill bacteria. They work far better, but remember, your skin is mostly bacteria so it’s hard on your skin. There’s a reason why nurses hands look they’re 90 years old. But even then, you can culture bacteria straight from the bottle. Not a lot, but with how fast bacteria grow, it’s enough.
One of my favorite statistics is this: You know the bleach wipes that kill 99.9% of bacteria? What’s 0.01% of 100 trillion? Everything, and I mean everything, is covered in bacteria. NASA missions to Mars that can’t risk contaminating Mars with bacteria from Earth don’t even get close – they just assume that when they land somewhere, you won’t be able to look for life after a certain point because the risk of contamination is high. The second you pull things out of the autoclave, they have bacteria from the air land on them. There’s bacteria that can survive space, that can survive underwater vents with temperatures and pressures that make pressure cookers look comfortable, and that can survive on any place we’ve ever found on this planet.
https://slate.com/news-and-politics/2007/01/is-soap-self-cleaning-because-it-s-soap.html
*How clean is bar soap in a public bathroom? Is it “self-cleaning,” since it’s soap? It seems like a health hazard to me.*
>It’s dirty, but that doesn’t make it a health hazard. Soap can indeed become contaminated with microorganisms, whether it’s in liquid or bar form. According to a series of tests conducted in the early 1980s, bars of soap are often covered with bacteria and carry a higher load than you’d find inside a liquid dispenser. But no one knows for sure whether this dirty soap will actually transfer its germs to your hands during a wash.
> In fact, what little clinical evidence there is suggests that dirty soap isn’t so bad. A study from 1965 and another from 1988 used similar methodologies: Researchers coated bars of soap in the lab with E. coli and other nasty bacteria, and then gave them to test subjects for a vigorous hand-wash. Both teams found no transfer of contamination from the dirty soap. However, both studies were tainted by potential conflicts of interest: The first was conducted by Procter & Gamble, and the second came from the Dial Corp.
>Still, there’s no good evidence to contradict these studies, and it’s likely that the bacteria on a dirty bar would just wash off when you rinsed your hands. In other words, you’d be cleaning the soap as you cleaned your hands. (Your hands would probably have been a lot dirtier than the soap to begin with.)
There’s cleaning, disinfecting and sterilizing. A bar of soap just cleans, and does so by removing dirt and oil.
There are medicated body washes that fight bacteria for things like acne, but plain old soap won’t do all that.
So no, it is clean as long as you wash it off after use, but it is not disinfected or sterile and neither are you. Which is fine.
Source
-worked in infection control in a hospital
Soap needs water to work. It does that by “wrapping up” particles of grime, bacteria and so forth in small balls of soap molecules. Those balls float around in the water you’re washing in and get rinsed away, taking the dirt with them. But to make those balls, the soap molecules need to be in water, both because that’s part of why they make balls in the first place and also simply to be able to move about and cluster. So everything works when you lather the soap up in water, but if the soap’s in a solid bar, it doesn’t. So whatever’s on the surface of the bar is free to stay there.
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