Sodium Lauryl Sulfate (SLS) is a harsh (caustic) detergent.  Also known as a surfactant, which breaks down the surface tension of water. "It can actually damage the outer layer of the skin, the stratum corneum, causing dryness, roughness, scaliness, fissuring, loss of flexibility and reduction of the barrier functions of normal healthy skin.  The lipid dissolving action of some detergents, including SLS cause damage to the moisture retaining ability of the cellular level resulting in water loss and loss of water-binding ability" (Cosmetic Science, C. Prottey, 1978)

Sodium lauryl sulfate, a surface active agent and a common surfactant used in shampoos, was found to increase the absorption of certain chemicals.  Simply put, SLS in your shampoo could be increasing the rate of skin absorption of other chemicals in your shampoo and conditioner which may include preservatives, fragrances and color additives. (Cosmetic and the Skin, F.V. Wells, Reinhold Publishing Corporation, New York, 1964)

Sodium Lauryl sulfate (SLS) is used in concrete floor cleaners, engine degreasers, car wash detergents.  Along with hundreds of personal care products including probably every major brand of toothpaste you can find.

Cosmetics and personal care products containing Sodium Lauryl Sulfate:

• could keep children's eyes from developing properly.   Children under six are especially vulnerable to improper eye development;

• can cause cataracts in adults and delay healing of wounds on the cornea;

• can build up and cause major problems in the heart, liver, lungs and brain;

• can cause roughness and flaking of the skin;

• is a caustic cleanser that could corrode the hair; 

• is routinely used in clinical studies to deliberately irritate the skin so the effects of other substances can be tested.

A report from the Journal of the American College of Toxicology; Vol. 2, No. 7, 1983 states,

• SLS is routinely used in clinical studies to irritate skin tissue. 

• SLS corrodes hair follicle and impairs ability to grow hair.

• Carcinogenic Nitrates can form when SLS interacts with other nitrogen bearing ingredients.

• SLS enters and maintains residual levels in the heart, liver, lungs and brain from skin contact. (Shampoos?)

• SLS denatures protein, impairs proper structural formation of young eyes - damage permanent.

• SLS can damage the immune system; cause separation of skin layers and cause inflammation to the skin.  

Many medications are now administered through patches on the skin or by placing drops under the tongue.  Do you feel that it would be healthy to have chemicals such as Propylene Glycol and Sodium Lauryl Sulfate making contact with your body multiple times a day?

Studies are ongoing in this area. SLS is cheap and available and cost is definitely a factor when manufacturers are deciding on their formulations.  The irony is that we as consumers rarely see any of this saving and pay high prices for products that contain the same cheap ingredients as a lower priced product that doesn't have the benefit of a well known name and a huge advertising budget.  There are safer products on the market.  There are safer alternatives to SLS but they can cost up to ten times more than SLS.  One manufacturer said "I know it's not a good ingredient, but everyone uses it."

It has been shown in most cases to be extremely dangerous to your health.   In most cases the cap on the bottle costs more than the ingredients inside.

2002 Dr. Sam Epstein's Explanation to the Hazards of SLS - Sodium Laurel Sulfate 

Following is Dr. Epstein's answer regarding the degree of SLS toxicity. 

Regarding  Sodium Lauryl Sulfate, there is no evidence that SLS is carcinogenic. However, contrary, SLS is a harsh ionic detergent which is a strong irritant to skin, depending on concentration and the duration of exposure. The Cosmetic Ingredient Review (CIR) 2000 Compendium, of the Cosmetic, Toiletry and Fragrance Association, admits that SLS "causes severe epidermal changes--of the skin of mice--(indicating) a need for tumor-enhancing activity assays," (1). The Compendium also admits that SLS containing products are "designed for brief discontinued use, following which they are thoroughly rinsed from the surface of the skin." Furthermore, as reported in model studies, published by the Danish Institute of Public Health, a single 24-hour exposure of SLS to human skin damages skin protein and causes prolonged disruption of "the skin barrier integrity of the skin," to allow the penetration of carcinogens such as nickel and chromate (2,3). Thus, skin absorption of the multiple carcinogenic ingredients commonly found in mainstream industry cosmetics and toiletry products (4), including shampoos, could be greatly increased by SLS type detergents.  Clearly, the American Cancer Society is unaware of this information, besides the fact that mainstream industry cosmetics and toiletries contain a wide range of carcinogenic ingredients, precursors, and contaminants, besides ingredients that break down to release carcinogens such as formaldehyde.  Furthermore, laureths, besides other ethoxylated alcohols, are generally contaminated by the volatile carcinogen 1,4-dioxane, as admitted by the CIR Compendium (1), and also the carcinogen ethylene oxide. Samuel S. Epstein, M.D. 1. CTFA. Cosmetic Ingredient Review (CIR) Compendium 2002. 2. Nielsen, G.D. et al. Effects of Industrial Detergents on the Barrier Function of Human Skin. Int. J. Occup. Med. 6(2):138-142, 2000. 3. Nielsen, G.D. Effects of Four Detergents on the In-Vitro Barrier Function of Human Skin. Int. J. Occup. Med. 6(2):143-147, 2000. 4. Epstein, S.S. and Steinman, D. The Safe Shopper's Bible. Macmillan/Hungry Minds, Inc., New York, 1995. 5.  Unreasonable Risk, Avoidable Risks of Cancer, 2002. 6.  Unreasonable Risk, 2nd edition, 2005 7.  Cancer Gate- How to win the Losing Cancer  War