Ingredient review

Sodium Laureth-40 Sulfate

INCI: Sodium Laureth-40 Sulfate

A milder relative of sodium lauryl sulfate that effectively cleanses without stripping the skin.

beautyskincarecleanser

In plain English

Sodium Laureth-40 Sulfate is a cleansing ingredient made from coconut or palm oil. It's a gentler version of sodium lauryl sulfate (SLS) because it has extra ethylene oxide units that make it less irritating. It helps water mix with oil and dirt so they can be rinsed away, leaving skin and hair clean. Because it's mild, it's often used in products for sensitive skin or daily use.

Review score

Safety, usefulness, and evidence

3.5Good
3.5/ 5

Potentially useful with some tradeoffs

The evidence base is useful, but some claims depend heavily on the formula.

Risk flags are low for most users, though the finished product can still irritate.

Source
synthetic
Evidence
moderate
Irritation
low
Clogging risk
low
How reviews are scored

Quick decision guide

Useful, but context matters

Sodium Laureth-40 Sulfate is generally a lower-concern ingredient when the full formula suits your skin.

Plain-English read

Treat this as a practical screening step before you compare products that contain this ingredient.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging Sodium Laureth-40 Sulfate.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. Step 3If a product stings, breaks you out, or worsens irritation, judge the finished formula and stop using it even if the ingredient scores well.

Score terms in plain English

Irritation risk

low

Less likely to sting, burn, or bother most users, though sensitive skin can still react.

Clogging risk

low

Less likely to feel heavy or contribute to clogged pores for most skin types.

Evidence level

moderate

There is useful support, but formula details and claim strength still matter.

What it is

A synthetic surfactant derived from fatty alcohols (from coconut or palm oil) that has been ethoxylated (treated with ethylene oxide) to reduce its harshness. The '40' indicates the average number of ethylene oxide units, making it significantly milder than standard SLS.

How it works

It lowers the surface tension between water and oil, allowing dirt, sebum, and makeup to be emulsified and rinsed away. Its large molecular structure and ethoxylation make it less penetrating and less irritating to the skin barrier than shorter-chain sulfates.

Pros

Milder than SLS

The ethoxylation process makes this surfactant much less irritating than sodium lauryl sulfate, so it's suitable for daily use on most skin types.

Effective foaming cleanser

It produces a satisfying lather that helps spread the product evenly, making cleansing feel thorough and pleasant.

Cons and cautions

Potential for 1,4-dioxane contamination

During manufacturing, trace amounts of 1,4-dioxane can form. Reputable brands purify their ingredients to remove this contaminant, but it's worth checking for third-party testing.

Not ideal for very dry skin

Even though it's mild, it can still strip natural oils if used too frequently or on already dehydrated skin, leading to tightness.

Best for

  • People with normal to oily skin looking for a gentle daily cleanser
  • Those who find SLS too drying but still want a foaming cleanser

Use caution if

  • Individuals with severely compromised skin barriers or active eczema should opt for non-sulfate cleansers

Usage tips

Use in rinse-off products only; avoid leaving on the skin for extended periods.
Follow with a moisturizer to replenish any lost hydration.
If you have sensitive skin, patch test a new product containing this ingredient before full use.

Safety summary

Sodium Laureth-40 Sulfate is considered safe for use in cosmetics at typical concentrations. The main safety consideration is the potential presence of 1,4-dioxane, which is strictly limited by regulations. Reputable manufacturers use purification steps to keep levels well below safety thresholds. Overall, it poses low irritation and comedogenic risk.

Research notes

Research indicates that ethoxylated sulfates like SLES are significantly less irritating than non-ethoxylated SLS. The CIR panel has reviewed data and concluded that SLES is safe for cosmetic use. Studies on 1,4-dioxane show that trace amounts can be present, but regulatory limits (e.g., FDA guidance) ensure consumer safety.

Common label clues

Typical concentration
1–15% in rinse-off products; lower in leave-on formulas
Regulatory status
Approved for use in cosmetics by the FDA and the European Commission. The Cosmetic Ingredient Review (CIR) panel has deemed it safe when formulated to minimize 1,4-dioxane.
Common uses
Shampoos, Body washes, Facial cleansers, Bubble baths
Environmental note
Derived from renewable plant sources (coconut or palm oil), but the ethoxylation process is energy-intensive. Some palm oil sources may raise sustainability concerns.

Good to know

  • The '40' in the name refers to the average number of ethylene oxide units, which directly correlates with its mildness.
  • It is often used in combination with other surfactants to balance cleansing power and gentleness.

Common questions

What is Sodium Laureth-40 Sulfate in beauty products?

Sodium Laureth-40 Sulfate is a cleansing ingredient made from coconut or palm oil. It's a gentler version of sodium lauryl sulfate (SLS) because it has extra ethylene oxide units that make it less irritating. It helps water mix with oil and dirt so they can be rinsed away, leaving skin and hair clean. Because it's mild, it's often used in products for sensitive skin or daily use.

What does Sodium Laureth-40 Sulfate do in a beauty product?

It lowers the surface tension between water and oil, allowing dirt, sebum, and makeup to be emulsified and rinsed away. Its large molecular structure and ethoxylation make it less penetrating and less irritating to the skin barrier than shorter-chain sulfates.

Is Sodium Laureth-40 Sulfate safe for most people?

Sodium Laureth-40 Sulfate is considered safe for use in cosmetics at typical concentrations. The main safety consideration is the potential presence of 1,4-dioxane, which is strictly limited by regulations. Reputable manufacturers use purification steps to keep levels well below safety thresholds. Overall, it poses low irritation and comedogenic risk.

Who should be careful with Sodium Laureth-40 Sulfate?

Individuals with severely compromised skin barriers or active eczema should opt for non-sulfate cleansers

Research sources

Cosmetic Ingredient Review (CIR) - Safety Assessment of Sodium Laureth SulfateOpenFDA - 1,4-Dioxane in CosmeticsOpenPubMed - Irritation potential of SLS vs SLESOpen

Ingredient reviews are educational and are not medical advice. Patch test new products and ask a licensed clinician about persistent irritation, allergies, pregnancy-specific questions, or diagnosed skin conditions.