Sodium Laureth Sulfate (SLES): Is It Bad for Your Hair?
INCI: Sodium Laureth Sulfate · also listed as SLES, Sodium lauryl ether sulfate, Sodium laureth-2 sulfateThe sulfate in most shampoos on the shelf, and the one "sulfate-free" is defined against. Clearly milder than SLS, but a comparison is not a pass for every hair type.
Fine for most hair, still too much for some
SLES is SLS with ethylene oxide units added. The bulkier molecule gets into scalp skin far less easily, so it cleans nearly as well with a fraction of the irritation, and EU and US safety panels clear it for rinse-off use. On a normal or oily scalp with undamaged hair, it is a sensible default.
It is still an anionic sulfate. Over repeated washes it lifts the lipids between cuticle scales, fades colour faster and leaves porous or coily hair drier than a gentler system would. The 1,4-dioxane question is real, but it is a manufacturing issue, and modern levels are tiny.
- INCI name
- Sodium Laureth Sulfate (the "eth" marks the ethoxylation that makes it milder)
- Also on labels
- SLES, sodium lauryl ether sulfate. Same behaviour: sodium myreth sulfate, magnesium laureth sulfate, sodium trideceth sulfate.
- Job in hair care
- Primary anionic surfactant. Lifts sebum, sweat and styling residue off scalp and shaft, and builds the foam people read as "clean".
- Found in
- Most mass-market shampoos, 2-in-1s and body washes. Rare in conditioners.
- Typical level
- 5–15% of a shampoo, usually paired with a betaine that softens it further.
- Regulatory status
- Permitted in the EU, UK and US, no cosmetic limit. Its contaminant 1,4-dioxane is capped instead: ≤10 ppm EU benchmark, 1 ppm in New York.
- Hairmony class
- ActiveScored by the Hairmony engine, so it actually moves which products you get recommended.
- Scored for
- +clarifying+scalp oil control−colour retention−porosity repair−moistureA "moderate"-tier cleanser in the engine: a clarifying and oil-control positive, with smaller colour, porosity and moisture penalties than SLS carries.
What SLES does to hair and scalp
On the scalp it removes sebum and product efficiently but sits well below SLS on irritation scales: the added ethylene oxide units make it too bulky to slip through the skin barrier. Most scalps tolerate it daily.
On the hair shaft it behaves like the sulfate it is, just less so. Each wash takes some of the lipid that holds the cuticle flat. Bleached, high-porosity and coily hair loses that lipid fastest, and shows it first as frizz and fade.
Worth using if
- Your scalp is oily or you wash daily
- You use silicones or styling products that need a real cleanser
- Your hair is undamaged and low-to-medium porosity
Be careful if
- Your hair is bleached, coloured or high-porosity
- You have type 3–4 curls that dry out between washes
- A sensitive or eczema-prone scalp still flares on it
Where it sits on a shampoo label
In practice: if SLS is too harsh and sulfate-free leaves your scalp greasy, SLES plus a betaine is usually the middle that works. Coloured hair: roots only.
Is SLES harmful? The 1,4-dioxane question
The health claim attached to SLES is not about the surfactant but about a by-product of making it. Ethoxylation can leave traces of 1,4-dioxane, a probable carcinogen. That is why regulators cap the contaminant rather than the ingredient.
The context is scale. FDA surveys found average levels falling from 50 ppm in 1981 to mostly undetectable by 2008, because manufacturers vacuum-strip it out. The EU benchmark is 10 ppm, 1,4-dioxane evaporates readily, and a shampoo is rinsed off within minutes.
What we based this on
- Contamination levels. FDA surveys: average 1,4-dioxane fell from 50 ppm (1981) to 19 ppm (1997); by 2008, 80% of products tested had none detectable.
- Limits. EU SCCS benchmark ≤10 ppm; New York caps personal-care products at 1 ppm since December 2023. The surfactant itself: listed in CosIng, rated safe for rinse-off by the US Cosmetic Ingredient Review.
Not medical advice. This page describes how an ingredient behaves on hair and scalp. If you have a persistent rash, sores, sudden shedding or a diagnosed scalp condition, see a dermatologist before changing anything.
Frequently asked
Is sodium laureth sulfate the same as SLS?
No. SLES is SLS with ethylene oxide added, which makes it bulkier and much less irritating to scalp skin. It foams and cleans almost as well. If a shampoo lists SLES rather than SLS, it is the gentler of the two.
Does sodium laureth sulfate cause hair loss?
There is no evidence that it does. It does not reach the follicle during a rinse-off wash. It can leave porous or coily hair drier and more prone to snapping mid-shaft, and that breakage is often mistaken for shedding.
Is sodium laureth sulfate safe if it can contain 1,4-dioxane?
At modern levels, yes. 1,4-dioxane is a manufacturing trace, not an ingredient, and it is regulated: the EU benchmark is 10 ppm and New York caps it at 1 ppm. It also evaporates readily, and a shampoo is rinsed off within minutes.
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