What Is Sodium Lauryl Sulfate?

A 2023 review describes SLS as an anionic surfactant, the sodium salt of lauryl alcohol, used at usual concentrations of 0.5 to 2 percent as a detergent in house cleaning and dishwashing products and soaps, in cosmetics, shampoos and hand soaps, and for more than 50 years in toothpastes. A 2019 commentary in the British Journal of Dermatology says SLS, also called sodium dodecyl sulfate, is used in many household and hygiene products and has an irritating effect on skin, so it is used extensively in models for testing how skin responds to irritants.

The Cosmetic Ingredient Review panel's 1983 assessment found SLS and ammonium lauryl sulfate are irritants in patch testing at concentrations of 2 percent and greater, that irritation increases with concentration, and that the longer they stay in contact with skin, the greater the likelihood of irritation. It concluded they appear to be safe in formulations designed for discontinuous, brief use followed by thorough rinsing, and that products intended for prolonged skin contact should not exceed 1 percent.

SLS is not the same as sodium laureth sulfate, or SLES. A 2022 systematic review says SLES is closely related to SLS, but that in terms of irritant potential SLES, in contrast to detergents such as SLS, can be described as mild.

The 1,4-dioxane question is about other ingredients. The FDA says 1,4-dioxane is not a cosmetic ingredient but can form as a byproduct when making certain detergents, foaming agents, emulsifiers and solvents identifiable by PEG, polyethylene, polyoxyethylene, -eth- or -oxynol- in their names, a naming pattern that fits sodium laureth sulfate but not sodium lauryl sulfate. The FDA calls 1,4-dioxane a potential human carcinogen and says its monitoring shows manufacturing changes have significantly reduced levels in cosmetics over time. New York's environmental agency describes state limits of 2 ppm as of December 31, 2022 and 1 ppm as of December 31, 2023 for household cleansing and personal care products, and 10 ppm for cosmetics.

Sources checked September 15, 2026. Every point below links the page it came from.

The sources behind this answer

  • StudyA 2023 review describes SLS as an anionic surfactant used at 0.5 to 2 percent in cleaning products, soaps, cosmetics and shampoos, and for more than 50 years in toothpastes. Journal of Dentistry, Shiraz University of Medical Sciences, via PubMed Central ↗
  • StudyA 2019 British Journal of Dermatology commentary says SLS irritates skin and is therefore used extensively in models for testing skin responses to irritants. British Journal of Dermatology, via PubMed Central ↗
  • StudyThe Cosmetic Ingredient Review's 1983 assessment found SLS is an irritant in patch testing at 2 percent and greater, with irritation rising with concentration and contact time. Cosmetic Ingredient Review ↗
  • Medical referenceThe CIR panel concluded SLS appears safe in formulations for brief, discontinuous use followed by thorough rinsing, and at no more than 1 percent in products for prolonged skin contact. Cosmetic Ingredient Review ↗
  • StudyA 2022 systematic review says sodium laureth sulfate is closely related to SLS but, unlike SLS, can be described as mild in irritant potential. International Journal of Environmental Research and Public Health, via PubMed Central ↗
  • Government sourceThe FDA says 1,4-dioxane is not a cosmetic ingredient but can be a trace byproduct of ingredients identifiable by PEG, polyethylene, polyoxyethylene, -eth- or -oxynol- in their names. US FDA ↗
  • Government sourceThe FDA calls 1,4-dioxane a potential human carcinogen, citing NTP's finding that it is reasonably anticipated to be a human carcinogen and EPA's likely carcinogen classification. US FDA ↗
  • Government sourceThe FDA cites an EU scientific committee finding that 1,4-dioxane at 10 ppm or less in cosmetics is considered safe, and says its monitoring shows levels have declined significantly. US FDA ↗
  • Regulatory filingNew York's DEC describes 1,4-dioxane limits for household cleansing and personal care products of 2 ppm as of December 31, 2022 and 1 ppm as of December 31, 2023. New York State Department of Environmental Conservation ↗
  • Regulatory filingNew York's DEC policy refers to a maximum 1,4-dioxane trace concentration of 10 ppm for cosmetic products. New York State Department of Environmental Conservation ↗

Sources checked September 15, 2026. A brand statement is the company’s own claim, which we report but have not verified. Our grades are model-based estimates, not lab tests.

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