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Sodium lauryl sulfate

Sodium lauryl sulfate in skincare: Anionic surfactant, cleanser, foaming agent. What it does on skin, how strong the evidence behind the claim actually is, the concentrations in normal use, who reacts to it, and where it stands in pregnancy and sunlight. On a label it appears as Sodium Lauryl Sulfate; Sodium Laureth Sulfate.

Preservatives, surfactants and fragranceAnionic surfactant, cleanser, foaming agentEvidence: Strong

On the label: Sodium Lauryl Sulfate; Sodium Laureth Sulfate. Also called: SLS; SLES is the ethoxylated relative.

This is an ingredient reference, not a diagnosis and not a treatment plan. It describes what substances are and what the published evidence supports; it does not tell you what your skin has or what to put on it. A rash that spreads, hurts, weeps, does not settle, or comes with feeling unwell is a reason to see a doctor or pharmacist, not to change serum.

What it is

Two related anionic surfactants that do the cleaning and the foaming in a very large share of shampoos, washes and toothpastes. Sodium lauryl sulfate is the blunter of the two; sodium laureth sulfate has ethylene oxide units added, which makes it milder on skin while keeping the lather. Confusingly similar names, meaningfully different behaviour.

What it does on skin

They lift oil and dirt into water and produce foam, which does no cleaning but is what people judge a cleanser by. In doing so they also remove some of the skin's own lipids, which is where irritation comes from. Sodium lauryl sulfate does this so predictably that it is the standard irritant used in research to induce and study experimental irritant dermatitis.

What the evidence is worth

Evidence: Strong

Their cleaning function and their irritancy are both well characterised, and the relative mildness of the ethoxylated version over the plain one is consistent across studies. The concern that gets far more attention online — carcinogenicity — has no support: it originates in a 1990s chain letter and has been repeatedly checked and rejected.

How it is used

In rinse-off products, contact time is short and irritancy is limited for most people. If your hands, scalp or face are dry and reactive, a cleanser built on gentler surfactants is a reasonable change to try, and it will cost you lather. Leave-on products do not use these surfactants at meaningful concentrations.

Typical concentration in normal use: A few per cent up to double digits in cleansers. That is a description of the market, not a recommendation, and it is not a dose.

Who reacts to it

Cumulative irritant dermatitis rather than allergy: tightness, dryness, chapping and flare-ups of eczema, especially on hands washed many times a day. A separate, well-described observation is that some people prone to recurrent mouth ulcers report fewer of them on toothpaste without sodium lauryl sulfate, which is a cheap experiment for anyone who gets them often.

Pregnancy and breastfeeding

Generally considered fine

No pregnancy concerns.

Sunlight

No change

No effect on light sensitivity, though skin stripped by harsh washing is generally more reactive to everything, sunlight included.

Rules and labelling

Both are permitted. The genuine technical issue is with the ethoxylated version: ethoxylation can generate traces of 1,4-dioxane as a by-product, which manufacturers remove by vacuum stripping and which regulators monitor as a contaminant specification rather than as an ingredient.

What it goes with, and what it does not

Nothing to combine. The useful decision is upstream: how often you wash, how hot the water is, and whether you moisturise straight afterwards, all of which matter more to irritated hands than which surfactant is in the bottle.

One thing people get wrong

The myth is that SLS causes cancer, and it comes from a chain email that circulated in the 1990s and never quite died. It does not. The real, boring, documented issue is irritation from repeated exposure — which is a genuine reason to choose a gentler cleanser, and an entirely different claim from the one on the poster in the health-food shop.

Sources: EU Cosmetics Regulation (EC) No 1223/2009 and its annexes, as published in the European Commission's CosIng database, for every statement about what is permitted, restricted or banned · opinions of the Scientific Committee on Consumer Safety (SCCS) and safety assessments of the Cosmetic Ingredient Review (CIR) for the concentration positions · standard dermatology reference material for mechanism, tolerability and contact-allergy patterns · checked 2026-09-06. Deep links are deliberately omitted where a stable public URL could not be confirmed.

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