Soap-Free Soap?

November 18, 2007 8:01 PM

How can a bar of soap or bottle of shampoo be "soap free"?

I see commercials about how dove bars are "soap free" and when in the drug store, I see "soap free" baby wash. How is that possible? How does one clean without soap?

posted by ooklala to clothing, beauty, & fashion (13 comments total)

I think it means the pH is more neutral. Maybe they don't contain lye?
posted by hjo3 at 8:04 PM on November 18, 2007

Traditionally, a "soap" is a fatty acid treated with a base to produce an ionic surfactant. Detergents of other composition can be considered soap-free if you use this strict definition. This is all explained in the wikipedia entries for soap and detergent.
posted by mr_roboto at 8:13 PM on November 18, 2007

It depends on how they're defining "soap." They could just be using a different kind of surfactant that is less common than most brands.
posted by Cool Papa Bell at 8:13 PM on November 18, 2007

Dove does claim their bars are 100% moisturizer. That's very possibily erroneous, but it could explain that case.
posted by phaded at 8:22 PM on November 18, 2007

Seconding the "doesn't contain lye" theory. My doctor advised me against using anything that contained the word "soap" int he description, due to my dry skin. Any cleaning product I buy is usually called a "beauty bar," it's basically just a gentle cleanser.
posted by piratebowling at 8:23 PM on November 18, 2007

It looks like Dove's "soap free" products don't contain sodium tallowate or sodium palmitate, while the other products do. The soap free stuff has other surfactants like Cool Papa Bell suggests--e.g. ammonium lauryl sulfate.

Oh, and soap doesn't contain lye, but lye (sodium hydroxide--very dangerous) plus animal fat = sodium tallowate. I'm vastly over-simplifying here.
posted by sevenless at 8:25 PM on November 18, 2007

When it's not really soap?

There are lots of cleansers and detergents that don't contain real soap (fatty acid salts); we call them "soap" anyway, because they serve the same function, but they're entirely chemically different.

If you look at the list of surfactants on Wikipedia, you'll see that true 'soap' is only one category of a fairly long list. Your non-soap skin cleanser probably contains one of the other ones from that list, combined with some moisturizers and filler.
posted by Kadin2048 at 8:37 PM on November 18, 2007

Historically, most soap was made by treating animal fat (usually tallow) with lye (sodium hydroxide) or potash (potassium hydroxide).

I think the point of the "no soap" claim is the implication that there's no animal fat in the product.
posted by Steven C. Den Beste at 8:45 PM on November 18, 2007

One advantage of using only detergent based cleansers in the bath is that you don't get soap scum, which is a chemical reaction between soap and hard water.
posted by happyturtle at 10:33 PM on November 18, 2007

I remember one of the selling points of Zest when it was first introduced was that it wasn't soap. Basically, you're looking at a detergent.
posted by kindall at 11:00 PM on November 18, 2007 [1 favorite]

I think the point of the "no soap" claim is the implication that there's no animal fat in the product.

Marketing-wise, "soap-free" indicates that the product is gentle. Soap is irritating to sensitive or dry skin. Non-soap-surfactant products are called "cleanser" versus "soap."
posted by desuetude at 7:55 AM on November 19, 2007

I would've hoped it meant 'not saponified,' but. I am allergic to soap, and would not go anywhere near Dove, no matter how nice their claims. It's soap, I say.
posted by kmennie at 9:11 AM on November 19, 2007

though it may not seem like it at first, the video on this page will totally explain it.
posted by snofoam at 9:30 AM on November 19, 2007