The Truth About...Sodium Lauryl Sulfate

Sodium lauryl sulfate (SLS), also known as sodium dodecyl sulfate, has been taking a beating in the PR department. In the last few years, sulfate-free alternatives to traditional hair products have been cropping up on store shelves and a number of articles and emails have spread word across the Internet that the chemical causes cancer.

"To some extent this is an issue of marketing hype," says Paradi Mirmirani, a dermatologist with The Permanente Medical Group in Vallejo, Ca., "There is no evidence that sulfate-containing shampoos are harmful."

Foam and function
SLS is found in much more than shampoo. The ubiquitous chemical is present in hundreds of cosmetic, industrial and food products.

Deodorant, some makeup, shaving cream, bubble bath, mouthwash and shampoo all list SLS as an ingredient. It's also used to clean public eating places and food-processing machinery. In high concentrations, SLS can degrease an engine. The chemical is even found in (no joke) marshmallows.

The physical properties, i.e. a good and foamy lather, that consumers have learned to associate with with cleansing are the result of SLS. Because SLS is a surfactant, it is able to interact with surfaces, such as the skin, and "lift" particles off a surface without actually affecting the surface. By itself, water can only eliminate about 65 percent of substances like oil, bacteria and dirt.

Reports of the superiority of SLS as a cleanser date back to at least the 1930s, according to the Food and Drug Administration. Used in toothpaste, the chemical emulsifies food particles that would otherwise stick to teeth. When used in mouthwash, SLS competes with bacteria that would otherwise attache to tooth enamel and lead to plaque buildup.

Safe suds 
Despite serious claims about the hazards of SLS, there is no evidence to back them up. If someone accidentally swallows mouthwash, for example, SLS is quickly broken down by the liver. As for its use in shampoos, soaps and shaving creams, its chemical structure prohibits absorption through the skin.

Furthermore, the International Agency for the Research of Cancer, the Environmental Protection Agency and the FDA have all concluded that SLS does not cause cancer. The American Cancer Society also states on their website that SLS is a "known irritant, but not a known carcinogen."

It is true, however, that SLS can cause slight skin irritation. For this reason, many products, including the dermatologist-recommended facial cleanser Cetaphil, incorporate moisturizers and other ingredients to counteract these effects.

No one is advocating dousing yourself in sodium lauryl sulfates but, says Mirmirani, "They do provide a good lather."