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Chapter 1: Anionic surfactants

Sodium lauryl sulfate (SLS)

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Also called
sodium dodecyl sulfate
Found in
cleaners, shampoo, bubble bath, toothpaste

The worst fact: when scientists need to irritate human skin on purpose, SLS is what they use. It's the standard benchmark irritant in human skin-irritation tests. Australia's Poisons Standard lists it, but products with 30% or less are exempt, and above 5% they must carry eye and skin first-aid warnings. We found no household product above 30%.

Why brands use it: it's cheap and makes lots of foam. The foam itself does very little of the cleaning.

Take care if: you have eczema, get mouth ulcers, or have sensitive eyes. The UK medicines regulator warns that a moisturiser containing SLS may irritate the skin of children with eczema, possibly because of the SLS. Switching to an SLS-free toothpaste reduced ulcers in small studies.

Comes from: coconut or palm kernel oil, or petroleum.

Myth check: "SLS causes cancer": no good evidence, and regulators found it doesn't damage DNA. "It builds up in your body": no, very little gets through the skin, and what the body does absorb is mostly passed out in urine. The irritation is real.

Contaminants: nil.

Fair to say: it's considered safe when it's rinsed straight off. The longer it stays on skin, the more it irritates.

Correct as of November 2026. What the badges mean

Sources

  • Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for each chemical and for benzene and ethylene oxide. hcis.safeworkaustralia.gov.au
  • AICIS. Evaluation statement EVA00146: alkyl sulfates (2024). industrialchemicals.gov.au
  • NICNAS. IMAP Tier II assessments: sodium, ammonium and potassium lauryl sulfate (2013); sodium and ammonium laureth sulfate. industrialchemicals.gov.au
  • US Cosmetic Ingredient Review. Final report on sodium lauryl sulfate and ammonium lauryl sulfate (1983); sodium alpha-olefin sulfonates (1998); sodium cetearyl sulfate and related alkyl sulfates, incl. sodium coco-sulfate (2010).
  • UK MHRA. Drug Safety Update: aqueous cream may cause skin irritation (2013). gov.uk
  • Alli BY et al. SLS-free dentifrices and recurrent aphthous stomatitis: systematic review. J Oral Pathol Med 2019;48:358-364.
  • Löffler H, Happle R. Skin irritation by SLS, SLES and alkyl polyglucoside. Contact Dermatitis 2003.
  • University of Bristol, School of Chemistry. Molecule of the Month: sodium lauryl sulfate.

The full source list is at the end of Chapter 1.