Wait...What Exactly Are Sulfates? “Sulfates are detergents and they’re extremely good at what they do, cleansing hair and the scalp by cutting through dirt and grime,” says Ni’Kita Wilson, a cosmetic chemist in New Jersey. The most common sulfates you’ll spot in ingredient lists are sodium lauryl sulfate (a.k.a. SLS) and ammonium lauryl sulfate (a.k.a. ASL). What’s in Sulfate-Free Shampoos, Then? The short answer: Mild detergents that don’t completely wash away your hair’s moisture. They have names that are a mouthful and sound similar to sulfates, like sodium lauryl sulfoacetate. And unlike traditional shampoos, sulfate-free ones don’t froth or create as many suds. “Sulfate-free systems are more difficult to thicken, which means that chemists have to add more ingredients to make a nice product," says Wilson. "Otherwise your shampoo would flow like water."