Sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES) are commonly used in shampoos and cleansers to help give these products a bubbling and foaming effect. Belonging to the family of ethoxylated ingredients, both SLS and SLES’s biggest issue is that they can be highly irritating to the skin and the reason you react to a new product. They also carry a risk of contamination with 1,4-dioxane, a known carcinogen.