Why is "sulfate-free" a selling point for shampoo?

[No umlaut for U]

Of all the chemical families, I think of sulfate salts as among the most innocuous. Yet, especially in a Whole Foods or similar store, most of the shampoos boast of sulfate free formulae. What am I missing? What's the advantage?

[lexi]

Some people are allergic to the sulfates in shampoo, if I use a regular shampoo my scalp will be painfully itchy, and I have scratched so bad I've made my scalp bleed.
Also the sulfate salts strip colour more than sulfate free shampoos.

[ClaytonThroop]

Googling around seems to suggest that it's usually touted as gentler on colors, though I didn't find anything that really substantiates that.

It reminds me of this comic though
http://www.xkcd.com/641/

[Ferret Herder]

From what I've read, sodium lauryl sulfate (http://www.cosmeticscop.com/cosmetic-ingredient-dictionary/definition/1396/sodium-lauryl-sulfate.aspx) can cause allergic reactions or irritation, while sodium laureth sulfate (http://www.cosmeticscop.com/cosmetic-ingredient-dictionary/definition/1391/sodium-laureth-sulfate.aspx) is mild and gentle. Since they're often used together and are easy to confuse as well, I suspect they get tarred with the same brush.

[WhyNot]

There's also a very popular book out now called Curly Girl (http://www.amazon.com/Curly-Girl-Lorraine-Massey/dp/0761123008), which is an owner's manual for curly and wavy hair, aimed at people who hatehatehate their frizz, or (like me) grew up with straight hair and discovered it's actually wavy/curly.

In it, the author writes:
You'd never dream of washing a good wool or cashmere sweater with just any old detergent. But most people don't think twice about applying shampoo to the priceless fiber that's sitting on top of their head. The problem is that shampoos have a dirty little secret: They contain harsh detergents suchas sodium lauryl sulfate, ammonium laureth sulfate, or sodium laureth sulfate, which are foaming agents found in dishwashing liquid and laundry detergent. Sure, they're good for pots and pans because they cut grease so effectively.

Your hair, on the other hand, needs to retain its natural oils to protect it and your scalp. Stripping them away deprives the hair of necessary moisture, amino acids, and antibodies, and makes it look dry, dull and lifeless.

<snip>

Shampoo isn't good for any hair, but for curly girls it's a disaster. That's because curly hair is so porous that it absorbs detergent like a sponge. Put it in your hair and it doesn't rinse out. The truth is that lathers don't really cleanse at all. Manufacturers put lathering agents into products so you'll buy into the joy-of-suds myth.

<snip>

I can't say this too often: You do not need to use shampoo. I'm not saying leave your hair dirty. You must still cleanse the hair and scalp, but as you read on, you'll see that I recommend doing so with a sulfate-free cleanser or botanical conditioner (derived from real plant extracts).
pp 11-12

She goes on to claim that frizz is due to the harsh action of vigorous lathering and sulfates on the cuticle and the drying effect, causing the cuticle to open wide "to reach out for moisture from the atmosphere, hence the frizz."


Now...there's a whole lot of non-citing going on there, and I don't want you to ask me for cites, because they're not my claims ;) but the argument is common and popular right now. As I'm doing research to figure out WTF to do with my suddenly curly hair, I see the same argument on nearly every webpage devoted to curly hair care. As long as people believe it, manufacturers will exploit that belief and sell them what they want - sulfate free shampoos.

[No umlaut for U]

Googling around seems to suggest that it's usually touted as gentler on colors, though I didn't find anything that really substantiates that.

It reminds me of this comic though
http://www.xkcd.com/641/

That was the one thing I had heard, and since it was irrelevant to me, I didn't pursue that area.
Like the comic!;)