Can soap be made dirty?
September 28, 2008 5:12 AM   Subscribe

Can an anti-bacterial bar of soap become "dirty?". . .

like, what if you dropped a bar of dial or the sort into say, a cat litterbox? After washing the physical residue off of said bar of soap, is it clean to use from hence forth out?
posted by ws to Health & Fitness (7 answers total) 2 users marked this as a favorite

Just because it says *anti-bacterial* it doesn't mean it can't become contaminated. If there are any anti-bacterial agents at all in the ingredients they would act as immediate germ eradicators working on the surface of dirt, but as a whole, wouldn't be immune to exposure to pathogens if it were to be mixed in to the compound itself.
posted by watercarrier at 5:19 AM on September 28, 2008

The effectiveness of antibacterial soap over regular soap is still very much up in the air. The major ingredient in soaps of any kind is SDS which is really good at removing oils and dirt from your skin. It's also really good at ripping open the membranes of cells be they human cells or bacterial cells, this agent is often used in research to rupture cells so scientists can isolate proteins, nucleic acids or any number of other things.

So essentially if you contaminate soap you're contaminating something designed to destroy the bacteria on it. Yeah, some bacteria will survive because invisible layers of grit and grime will protect them from actually touching the soap but give it a good washing, maybe until you see that the bar has physically reduced in size, and put it back in use. I probably wouldn't leave it for guests to use, but I wouldn't have a problem using it myself.
posted by Science! at 6:45 AM on September 28, 2008

Unless this is hypothetical... as cheap as a bar of soap is, why risk it?
posted by toomuchpete at 6:56 AM on September 28, 2008

Here ya go: a neat little study about bar soap contamination says bars of soap don't serve as fomites ... however, there's a risk that the "juice" around a soap bar in a dish with no drainage can harbor Pseudomonas.

Liquid soap, even with antibacterials added, can get contaminated by Pseudomonas spp., it's a huge problem in hospitals, contact lens solutions, and ear piercing gun disinfectants.

Pseudomonas infections are especially gross because often they turn neon colors due to the bacterial pigment. Also, the smell is kind of fruity -- so you look like you've been contaminated with gatorade and you smell like starburst.
posted by arabelladragon at 7:18 AM on September 28, 2008

Body wash and shampoos are made with SDS-relatives; bar soap (made by saponifying animal or vegetable fats, i.e triglycerides, by mixing them with lye) has a carboxyl group where SDSes have a phospahte group, and usually retains some or all of the glycerin produced in the reaction. Just saying, it's not the same stuff that's in your lysis buffer.
So, the major way that non-antibacterial soaps get bacteria off your skin is simply by facilitating mechanical removal, rather than messing them up (this is without going into the differences between human/animal cells and bacterial cells, which have some pretty fancy tricks that our cells don't for living in inhospitable environments).
posted by pullayup at 7:42 AM on September 28, 2008

It seems like the solubility of soap would tend to remove any surface contamination very quickly.
posted by smackfu at 10:23 AM on September 28, 2008

Straight dope has some dope on this topic. The antibacterial properties of soap are hogwash (pun intended). Assuming you rinse the soap off, you're killing the bacteria in the drain, not your hands.
posted by chairface at 11:53 AM on September 28, 2008

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