Sodium Lauryl Sulfate -
Is It a Problem?
By Melody Milam Potter, PhD (AltM DrMeL)
You've seen it on practically every detergent and shampoo label you've ever read --sodium lauryl sulfate (SLS) or its compatriot, sodium laureth sulfate (SLES), although the substance hides under a hundred aliases. You may have heard that SLS causes cancer, an idea which experts pooh-pooh. If you are confused about the safety of this common chemical whose production exceeds 1 million pounds in the US alone, no one would blame you.
Sodium lauryl sulfate is a sudsing agent synthesized from coconut oil that makes household detergents, shampoos, and toothpastes foam up and clean more effectively. It is inexpensive and combining it with salt thickens it, making it a very available and useful product for manufacturers.
There is disagreement among experts as to the toxicity of SLS. Many experts have come out in support of SLS, stating that there is no evidence of danger from its use in shampoos, toothpastes, and detergents. Health Canada and the Cosmetic Ingredient Review Expert Panel considers SLS safe for cosmetic use.
Nonetheless, the Environmental Defense Fund (Scorecard) disagrees, listing sodium lauryl sulfate as a suspected gastrointestinal and liver toxicant. The Safe Shoppers Bible describes SLS as an aggressive cleaning agent and notes that although SLES is milder in action, SLES can contain a contaminant, 1,4-dioxane, which is carcinogenic.
Other sources suggest that the presence of SLS may allow other chemicals in a product to be absorbed more readily. Because of its use as a surfactant to increase the performance of other ingredients in cleaning products, it only makes sense that SLS would enhance the absorption of other chemicals. And in fact, a search of the medical literature turns up a study (Baynes & Riviere, 1998) that showed SLS enhanced the absorption of carbaryl (Sevin) into skin. Another study (Baynes, et al. 1996) shows SLS enhancing absorption of benzidine, a bladder carcinogen, and a third study (Qiao, et al. 1996) demonstrates the potential of SLS in combination with other chemicals to increase the absorption of parathion, a highly toxic pesticide.
The search did not turn up any studies that directly implicated SLS as a carcinogen in itself. I must note here that the way we usually contact chemicals like SLS is in combination with other chemicals, although research studies rarely look at anything more than a single chemical at a time.
But the most direct danger from SLS seems to be its potential as a skin, corneal, and mucosal irritant, and as an allergen. Some dentists, substantiated by research, warn that some people can develop canker sores of the mouth as a result of sensitivity to SLS. Some may react dermatologically to the use of shampoos with SLS and those who are sensitive to coconut oil may be especially reactive.
Researchers have also demonstrated that SLS can actually increase the response to other allergens. There are, additionally, several studies which report corneal damage and thickening after contact with low levels of SLS. Individual reactions to the substance vary greatly, however, so some people may be much more sensitive than others.
The bottom line, then, is this: There are numerous chemicals in cosmetics and cleaning products that are more likely to be harmful to your health than SLS; for instance, nitrosamines and ingredients that break down to form formaldehyde and other carcinogens. However, less harmful chemicals like SLS may interact with them to increase the likelihood that these more toxic substances enter your body.
If you are concerned about SLS or SLES, or if you are sensitive to the substance, read labels carefully, know the synonyms of these chemicals (see below) and buy detergents, shampoos, and cleaning products that dont contain them. Also, you can switch to a SLS-free toothpaste like Rembrandt Natural or just use baking soda to brush your teeth. Most toothpastes formulated for young children are SLS-free. And keep shampoos containing SLS and SLES out of your and your childrens eyes.
Go to to find a list of over 100 synonyms for SLS, including dodecyl sodium sulfate, SDS, hydrogen sulfate, sodium salt, aquarex methyl, avirol 101, carsonol sls, conco sulfate wa, detergent 66, Dreft, dupanal, duponol, empicol, emersal, finasol, gardinol, hexamol, irium, maprofix, sipon, sulfopon wa 1, sodium dodecanesulfate.
Baynes RE; Riviere JE. 1998. Influence of inert ingredients in pesticide formulations on dermal absorption of carbaryl. Am J Vet Res 59(2):168-75.
Baynes RE; Brownie C; Freeman H; Riviere JE. In vitro percutaneous absorption of benzidine in complex mechanistically defined chemical mixtures. Toxicol Appl Pharmacol, 141(2):497-506.
Qiao GL; Brooks JD; Baynes RE; Monteiro-Riviere NA; Williams PL; Riviere JE. 1996. The use of mechanistically defined chemical mixtures (MDCM) to assess component effects on the percutaneous absorption and cutaneous disposition of topically exposed chemicals. I. Studies with parathion mixtures in isolated perfused porcine skin. Toxicol Appl Pharmacol 141(2):473-86.
Dr. Potter, along with Erin E. Milam, is co-author of Healthy Baby/Toxic World: Practical Ways to Protect Your Baby During Pregnancy and Infancy, 1999.
Post your comments and questions at the AltMed Message Center. Copyright 1999 Melody Milam Potter, PhD (AltM DrMeL)