Sodium lauryl sulfate, a surface-active agent 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 that 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 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. (Cosmetic Science, C. Prottey, 1978). Sodium Lauryl sulfate (SLS) is used in personal care products including probably every major brand of toothpaste you can find.
A report from the Journal of the American College of Toxicology; Vol. 2, No. 7, 1983 (Final Report On The Safety Assessment Of Sodium Lauryl Sulfate) 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.
- SLS denatures protein and impairs proper structural formation of young eyes.
- SLS can damage the immune system; cause separation of skin layers and cause inflammation to the skin.
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.