Sodium laureth sulfate, or sodium lauryl ether sulfate (SLES), is a detergent and surfactant found in many personal care products (soaps, shampoos, toothpaste etc.). SLES is an inexpensive and very effective foaming agent.
SLES has been shown to produce eye or skin irritation in experimental animals and in some human test subjects. Some products containing SLES have been found to contain low levels of the carcinogen 1,4-dioxane, with the recommendation from the FDA that these levels be monitored.
Chemical structure
Its chemical formula is CH3(CH2)10CH2(OCH2CH2)nOSO3Na. Sometimes the number represented by n is specified in the name, for example laureth-2 sulfate. The commercial product is heterogeneous in the number of ethoxyl groups, where n is the mean. It is common for commercial products for n= 3. SLES is prepared by ethoxylation of dodecyl alcohol. The resulting ethoxylate is converted to an half ester of sulfuric acid, which is neutralized by conversion to the sodium salt. The related surfactant sodium lauryl sulfate (also known as sodium dodecyl sulfate or SLS) is produced similarly, but without the ethoxylation step. SLS and ammonium lauryl sulfate (ALS) are commonly used alternatives to SLES in consumer products.
Application
SLES, SLS and ALS are surfactants that are used in many cosmetic products for their cleansing and emulsifying properties. They behave similarly to soap.
Toxicology
Irritation
Although SLES is considered safe at the concentrations used in cosmetic products, it is an irritant similar to other detergents, with the irritation increasing with concentration. SLES has been shown to produce eye or skin irritation in experimental animals and in some human test subjects. The related surfactant SLS is a known irritant, and research suggests that SLES can also cause irritation after extended exposure in some people.
Carcinogenicity
Toxicology research by the OSHA, NTP, and IARC supports the conclusions of the Cosmetic, Toiletry, and Fragrance Association (CTFA) and the American Cancer Society that SLES is not a carcinogen. The U.S. Environmental Protection Agency classifies 1,4-dioxane to be a probable human carcinogen (having observed an increased incidence of cancer in controlled animal studies, but not in epidemiological studies of workers using the compound), and a known irritant (with a no-observed-adverse-effects level of 400 milligrams per cubic meter) at concentrations significantly higher than those found in commercial products. Under Proposition 65, 1,4-dioxane is classified in the U.S. state of California to cause cancer.
1,4-Dioxane contaminant
Some products containing SLES have been found to contain low levels of the known carcinogen 1,4-dioxane, with the recommendation from the U.S. Food and Drug Administration that these levels be monitored. The FDA encourages manufacturers to remove 1,4-dioxane, though it is not required by federal law. [ Read More... ]
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