Sodium lauryl sulfate, or SLS, is a surfactant (for simplicity’s sake, think of a surfactant as something that creates bubbles in dish soap, toothpaste, shampoo, shower gel, etc.). There is conflicting evidence, but my research has made me believe that SLS is not a carcinogen, but it is irritating to some people’s skin. SLS sometimes appears on labels as “coconut-derived surfactant.”
Sodium laureth sulfate, or SLES, is another widely-used surfactant (also coconut-based), and is probably carcinogenic, as it is usually contaminated with 1,4-dioxane (this happens during its production).
A 2008 study by the Organic Consumers Association showed that many eco-friendly dish soaps contained 1,4-dioxane, which is a byproduct of the production of SLES. Most of these companies no longer use SLES, but Ecover is a notable exception. Some products containing SLS are manufactured on equipment used to produce SLES, resulting in 1,4-dioxane cross-contamination if the equipment is not cleaned properly. Seventh Generation claims that their dish soap no longer contains detectable levels of 1,4-dioxane, despite their use of SLS and initial cross-contamination problems.
Bottom line: I’m never okay with using products that contain SLES, but I’m basically cool with SLS if I can’t find an alternative product without it. Because of the 1,4-dioxane cross-contamination issues, products with neither SLS nor SLES should be the first choice.
Of course, none of the products in our online store contain SLES. I use products with SLS in my home, and recommend them as well, if SLS-free alternatives aren’t available. I do NOT recommend skin care products with SLS because of its potential as an irritant, but I think it is safe in things like laundry or dish soap. (if you hand wash a lot of dishes this might be something to consider.)