Ingredient review

Laureth-100

INCI: LAURETH-100

Laureth-100 is a gentle, high-foam surfactant and emulsifier that helps blend oil and water in cleansers and serums, with a very low irritation profile.

beautyskincaresurfactant

In plain English

Laureth-100 is a synthetic ingredient that helps oil and water mix together in your skincare products. It is a type of surfactant, which means it can help lift dirt and oil from your skin so they rinse away with water. Because it has a very large molecule, it stays mostly on the surface of your skin and is less likely to cause irritation compared to harsher cleansers. You'll find it in gentle cleansers, micellar waters, and some lightweight serums where it helps keep the formula stable and spreadable.

Review score

Safety, usefulness, and evidence

4.0Good

4.0/ 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

Laureth-100 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.

Step 1Start with the score, then check the irritation and clogging risk before judging Laureth-100.
Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
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

Laureth-100 is a polyethylene glycol (PEG) derivative of lauryl alcohol, with 100 ethylene oxide units. It belongs to the laureth family of surfactants, known for their mildness and ability to create stable emulsions.

How it works

In a cosmetic formula, Laureth-100 reduces the surface tension between oil and water, allowing them to mix into a stable emulsion. Its large molecular size means it does not penetrate deeply into the skin, instead working on the surface to help cleanse and condition without stripping natural oils.

Pros

Extremely gentle on skin

Because of its large molecular size, Laureth-100 stays on the skin's surface and is very unlikely to cause stinging or irritation, even for those with reactive skin.

Versatile formula stabilizer

It helps mix oil and water into a clear, stable solution, which is why it's a go-to for micellar waters and lightweight serums that need to stay uniform.

Cons and cautions

Synthetic origin

Laureth-100 is made from petroleum-derived ethylene oxide and lauryl alcohol, which may be a turn-off for consumers seeking natural or plant-based ingredients.

Lower foaming action

Compared to shorter-chain laureths, Laureth-100 produces less foam, which might not satisfy those who prefer a rich lather in their cleansers.

Best for

People with sensitive or easily irritated skin looking for a gentle cleanser
Anyone using micellar waters or lightweight serums that need a mild solubilizer

Use caution if

Those who strictly avoid synthetic or PEG-based ingredients in their skincare

Usage tips

Use in rinse-off products like cleansers and shampoos for best results; it works well with other mild surfactants.

For leave-on products like serums, keep the concentration low (under 2%) to avoid any sticky residue.

Safety summary

Laureth-100 is considered safe for use in cosmetics at typical concentrations. It has a very low irritation and sensitization potential. As with all PEG compounds, there is a theoretical concern about 1,4-dioxane contamination during manufacturing, but reputable suppliers purify their ingredients to meet safety standards.

Research notes

Research on laureth surfactants shows that longer ethylene oxide chains reduce skin penetration and irritation. The Cosmetic Ingredient Review (CIR) has concluded that PEG lauryl ethers are safe as used in cosmetics. No significant human or animal studies specifically on Laureth-100 were found, but the class is well-studied.

Common label clues

Typical concentration: 0.5% to 5%
Regulatory status: Approved for use in cosmetics in the EU, US, and many other regions. The Cosmetic Ingredient Review (CIR) panel has reviewed PEG ethers and found them safe for use in rinse-off and leave-on products at typical concentrations.
Common uses: Cleansers, Shampoos, Conditioners, Facial serums, Micellar waters
Environmental note: PEG-based surfactants may have variable biodegradability. Some studies indicate that longer-chain PEGs can persist in aquatic environments, though they are generally considered low in toxicity to aquatic life.

Good to know

Laureth-100 is often used in combination with other surfactants to balance mildness and cleansing power.
The number '100' refers to the number of ethylene oxide units, which makes it much milder than Laureth-4 or Laureth-23.

Common questions

What is Laureth-100 in beauty products?

What does Laureth-100 do in a beauty product?

Is Laureth-100 safe for most people?

Who should be careful with Laureth-100?

Those who strictly avoid synthetic or PEG-based ingredients in their skincare

Research sources

Cosmetic Ingredient Review (CIR) – Safety Assessment of PEG Lauryl EthersOpen PubChem – Laureth-100 (Compound Summary)Open European Chemicals Agency (ECHA) – Information on Laureth-100Open

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.