Sodium laureth sulfate
Sodium laureth sulfate (SLES) is the contracted name for sodium lauryl ether sulfate. You may find it listed as laureth-8 carboxylic acid, sodium salt; polyethylene glycol (5, 7, 12, 400, or 600) lauryl ether sulfate, sodium salt; sodium dodecylpoly (oxyethylene) sulfate; PEG-(5, 7, 8, or 12) lauryl ether sulfate, sodium salt; sodium polyoxyethylene lauryl ether sulfate; and sodium lauryl sulfate ethoxylate.
SLES is prepared by treating sodium lauryl sulfate (SLS) with ethylene oxide, a process called ethoxylation. Ethoxylation can create, as a product contaminant, an extremely dangerous chemical called 1,4-dioxane which is cancer-causing (see steareths, polysorbates, phenoxyethanol, PEG, and ammonium laureth sulfate for more information about 1,4-dioxane). In spite of this, SLES continues to be used in the formulation of antiperspirants, sun lotions, moisturizers, bubble bath liquid, mascaras, toothpastes, shampoos, mouthwashes, shaving creams, dish soaps, liquid hand soaps, and a variety of personal care items.
SLES functions mainly as a surfactant and an anionic detergent. It’s got a much greater foaming action than SLS because of the ethoxylation. It has unique wetting, dispersing, decontaminating, thickening, solvency and solubilizing properties. These properties are harnessed in the preparation of a wide range of commercial products including dyes, lubricants, degreasers, stain removers, carpet cleaners, glues, and foaming agents.
On exposure, SLES can dissolve the skin’s natural oil, creating a drying effect much the same way as it dissolves oils and greases in automobile engines. It’s known to denature skin proteins causing irritation and facilitating the deeper entry of environmental pollutants and unwanted chemicals in personal care products into more sensitive sections of the skin. It’s therefore not surprising that SLES has been found to exhibit comedogenic properties, i.e. it produces acne and pimples.
SLES is known for its hormonal disruption and estrogen-mimicking properties. It can lead to hair loss. SLES’s effects on the eye and other organs are much greater in children due to the ease with which it penetrates their skin. One grave concern is that the damaging effect on the eyes may be irreversible. Although it’s considered less irritating than SLS, it can stay in your tissues for quite a long time because it’s difficult for the liver to metabolize. It can therefore have a longer-lasting, adverse effect on the body.
When SLES reacts with nitrogen-based substances in the body, nitrates can be formed which may create carcinogenic conditions and/or produce allergic reactions. Given that SLES is an ethoxylated compound, there’s the chance that the contents of products containing such a chemical can be contaminated by carcinogenic 1,4-dioxane.
The Personal Care Products Council (formerly the Cosmetic, Toiletry, and Fragrance Association) has cautioned against prolonged use of products containing SLES unless they contain extremely low doses. But it’d be difficult to know how much is present given that ingredient concentrations are usually not listed on the product labels.
FYI, ammonium laureth sulfate, sodium pareth sulfate, and sodium myreth sulfate may be listed on your product instead of SLES. Just be aware that they perform a similar, if not the same, function and are just as harmful.