Sodium Laureth Sulfate

What it is

Sodium laureth sulphate is the most widely used cleansing surfactant in shampoos. It removes oil and dirt from the hair and produces the foam that most people associate with cleanliness. The “eth” in the name stands for a manufacturing step, ethoxylation: it makes the molecule milder than the closely related sodium lauryl sulphate, with which it is frequently confused.

That confusion is at the heart of the public debate. The two substances differ in exactly one respect, but that respect concerns irritant potential. People talking about “sulphates” often mean one and hit the other. For the assessment it therefore matters which of the two actually appears in the list.

Why

• Confusion with sodium lauryl sulphate is the most common error in this topic. Much of what circulates about “sulphates” comes from studies with the non-ethoxylated relative, which is more irritating. Transferring it without examination is inadmissible — the substances are related but not interchangeable.
• Why the classification reads “low risk”: because of the short contact time, the rinse-off application and the long history of use. Irritation is possible and occurs with a sensitive scalp or very frequent washing; that is a question of dose and frequency, not of basic tolerability.
• Cleansing always means removing oil. An effective surfactant also removes part of the skin's own oil film — that is not a fault but the function. A dry scalp after washing is therefore more a question of washing frequency and of the formulation as a whole than the fault of a single substance.
• “Sulphate-free” is a statement about a raw material, not about mildness. Sulphate-free formulations use other surfactants that bring their own properties and are not automatically better tolerated. Doing without is a trade, not a removal.
• Manufacture is a point of its own: ethoxylation can produce by-products that remain in the raw material. Manufacturers usually remove them, but the purity of the raw material cannot be read from the ingredient list — the same pattern as with cocamidopropyl betaine.

When the assessment differs

• Sensitive, irritated or eczema-prone scalp skin: the irritation threshold is lower here; washing frequency and formulation are the adjustable factors.
• Very frequent washing: the burden arises from the sum of applications, not from the single one.
• Eye contact: surfactants irritate the eyes; particularly relevant in practice with children.
• Products that stay on the skin: the classification expressly assumes rinse-off use and does not apply to other forms of application.
• Occupational contact: washing many heads daily means wet work and frequent surfactant contact on the hands — the most common cause of occupational skin problems in hairdressing.

Open questions

• Concentration in the actual product: not available. It largely determines how strongly the product cleanses and how much it irritates.
• Purity of the raw material used: not documented and not readable from the ingredient list. Limits and test procedures exist for by-products of ethoxylation; they have not been checked here and are not quoted second-hand.
• Direct comparison of irritant potential with sodium lauryl sulphate: not backed by data here. The statement above describes the structural difference, not the result of a test series.
• Regulatory status: not checked; statements on use and maximum levels are not quoted second-hand.

Related substances

Applies to: Surfactants

• Cocamidopropyl Betaine — Mild surfactant, cleansing

Further substances from the same group for which a long-form assessment already exists.