Sodium Laureth Sulfate

What it is

Sodium laureth sulfate is a detergent made by adding a few ethylene oxide units to lauryl alcohol before sulfating it. Those extra units make the molecule bulkier and less able to disrupt skin proteins than sodium lauryl sulfate (SLS). It is the workhorse foaming agent of shampoos and cleansers, and turns up in wash-off masks and cleansing balms rather than leave-on ones.

What it does well

• Cleans and foams efficiently at low cost

  It removes sebum, sunscreen and make-up reliably and produces the lather most people associate with 'clean', which is why it remains standard in rinse-off products.

  Strong evidence

• Measurably milder than sodium lauryl sulfate

  Head-to-head human washing studies distinguish the two: SLES produces less subclinical skin-surface disruption than SLS at comparable use. This is the evidence behind 'SLS-free' claims, though SLES is still a detergent, not a mild one in absolute terms.

  Moderate evidence

Worth knowing

• Can dry or tighten skin with frequent or prolonged contact

  Like all anionic sulfate detergents it removes some skin lipids and can raise water loss if used often, left on too long, or used in hot water. In a rinse-off mask used once or twice a week this is a minor issue.

  Matters most toPeople with dry, eczema-prone or sensitive skin, and anyone cleansing more than twice a day.

• Stings eyes

  It is a mucous-membrane irritant at cleansing concentrations, so keep wash-off masks away from the eye area.

  Matters most toEveryone using it near the eyes; contact-lens wearers in particular.

• 1,4-dioxane residue from the ethoxylation step

  Because SLES is ethoxylated, the raw material can contain traces of 1,4-dioxane. It is removed by vacuum stripping and controlled in the EU through the general ban on 1,4-dioxane as an ingredient plus the technically-unavoidable-traces rule; residues in finished products are typically at parts-per-million level and it is rinsed off.

  Matters most toConsumers comparing 'sulfate-free' claims; this is a supplier-quality issue rather than an inherent property.

Where the EU stands

Sources (3)

Every link goes to the original: a journal, a PubMed record or an EU document.

1. [1]
   Subclinical, non-erythematous irritation with an open assay model (washing): sodium lauryl sulfate (SLS) versus sodium laureth sulfate (SLES)

   Food and Chemical Toxicology · 2001 · doi:10.1016/s0278-6915(00)00132-0

   A realistic washing model could distinguish the two surfactants, detecting subclinical skin-surface changes and separating SLS from the milder SLES.

2. [2]
   Soapwort (Saponaria officinalis L.) Extract vs. Synthetic Surfactants-Effect on Skin-Mimetic Models

   Molecules · 2021 · doi:10.3390/molecules26185628

   Anionic surfactants including SLS and SLES dissolved substantially more skin protein and lipid than plant-derived alternatives in skin-mimetic models.

3. [3]
   The Role of TRPV1 Channel in Cosmetic Safety Evaluation

   ACS Omega · 2026 · doi:10.1021/acsomega.5c10830

   Anionic surfactants activated the skin's TRPV1 irritation pathway more than amino-acid-based and non-ionic surfactants, which were consistently milder.