What Is Sodium Lauryl Sulfate (SLS)?
In plain English: Sodium lauryl sulfate (SLS) is a strong, high-foaming anionic surfactant used in toothpaste, shampoo, dish soap and many household cleaners. It's a well-documented skin and eye irritant for some people — but, contrary to viral posts, it is not a proven carcinogen.
Also listed as: SLS, sodium dodecyl sulfate, sodium monododecyl sulfate
The honest science
SLS is one of the most-studied surfactants there is. Its job is to foam and cut grease, and it does that well — sometimes too well, stripping enough skin oil to cause redness, dryness or stinging, especially at higher concentrations or with long contact. 1 The higher the concentration and the longer it sits on skin, the more likely the irritation.
The cancer claim, though, is internet myth. A peer-reviewed toxicology review concluded there's no scientific evidence that SLS causes cancer, and major reviewers reached the same conclusion. 2 EWG gives SLS a low overall hazard score, with its main flag being skin/eye irritation rather than serious toxicity. 1 Confusion often comes from mixing SLS up with SLES, which is a different molecule with a real contamination concern.
Bottom line: SLS is an irritant, not a poison. Sensitive skin, eczema, or a mouth prone to canker sores are the real reasons to avoid it — not a cancer scare.
Where you'll find it
- toothpaste
- shampoo
- dish soap
- foaming cleansers
- bath products
- some surface cleaners
The safer-swap angle: If SLS leaves your hands dry or your mouth raw, gentler sugar-based surfactants clean well without the strip. See our full guide for the deeper story on SLS.
→ Read the full deep-dive guide on Sodium Lauryl Sulfate (SLS)
Frequently asked questions
Does SLS cause cancer?
No. A peer-reviewed toxicology review found no evidence that SLS is a carcinogen, and EWG rates it low-hazard overall. The cancer claim is a persistent online myth, often from confusing SLS with the ethoxylated ingredient SLES.
Why does SLS irritate my skin?
SLS is efficient at stripping oils, so at higher concentrations or with prolonged contact it can leave skin dry, red or stinging. People with sensitive skin, eczema, or frequent canker sores tend to react most.
Should I avoid SLS?
Only if it irritates you. It's a genuine irritant for some, but not a health emergency. If your skin or mouth reacts, choose gentler surfactants — but you don't need to fear it as a carcinogen.
Sources
- SODIUM LAURYL SULFATE — EWG Skin Deep — Environmental Working Group
- Human and Environmental Toxicity of Sodium Lauryl Sulfate (SLS): Evidence for Safe Use in Household Cleaning Products — PMC / Environmental Health Insights
Ingredient safety data changes as new research is published, and product formulas change over time. Always read the current label and check primary sources.
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