Ingredient review

PEG-100 Stearate

INCI: PEG-100 Stearate

A widely used synthetic emulsifier that helps create stable, smooth creams but may be less ideal for very sensitive or acne-prone skin in high concentrations.

beautyskincareemulsifier

In plain English

PEG-100 Stearate is a man-made ingredient that acts like a bridge between oil and water. In a moisturizer, it keeps the formula from separating into an oily layer and a watery layer, so you get a smooth, consistent cream every time you pump it. It's very common in drugstore and department store lotions because it's reliable and inexpensive.

Review score

Safety, usefulness, and evidence

3.8Good

3.8/ 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

PEG-100 Stearate 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 PEG-100 Stearate.
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

PEG-100 Stearate is a polyethylene glycol (PEG) derivative of stearic acid, a fatty acid found naturally in shea butter and cocoa butter. The 'PEG-100' refers to the number of ethylene oxide units attached, which makes the molecule water-friendly while the stearate part remains oil-friendly. This dual nature allows it to stabilize oil-and-water mixtures.

How it works

When you mix oil and water, they naturally want to separate. PEG-100 Stearate positions itself at the interface between oil droplets and water, with its water-loving (hydrophilic) head in the water and its oil-loving (lipophilic) tail in the oil. This reduces surface tension and keeps the droplets evenly dispersed, creating a stable emulsion that feels creamy and spreads easily on skin.

Pros

Excellent emulsifier

PEG-100 Stearate reliably prevents oil and water from separating, so your cream stays smooth and consistent from first use to last.

Widely tested and safe

It has been used for decades in thousands of products and is considered safe at typical use levels by major regulatory bodies.

Cons and cautions

Potential trace impurities

During manufacturing, small amounts of ethylene oxide or 1,4-dioxane (a possible carcinogen) can form. Reputable brands purify their ingredients to keep these levels extremely low.

Not natural or biodegradable

As a synthetic PEG compound, it does not break down easily in the environment and is not suitable for 'natural' or 'green' skincare lines.

Best for

Anyone using standard moisturizers or sunscreens
People who want a reliable, affordable cream texture

Use caution if

Those with known sensitivity to PEG compounds
People seeking fully natural or biodegradable formulations

Usage tips

Look for products that list PEG-100 Stearate near the middle or end of the ingredient list — that means it's used at a moderate level.

If you have very oily or acne-prone skin, try a lightweight gel or water-based moisturizer that uses alternative emulsifiers like Cetearyl Glucoside.

Safety summary

PEG-100 Stearate is considered safe for most people at the low levels used in cosmetics. The main concern is potential contamination with 1,4-dioxane, but reputable manufacturers purify their ingredients to meet safety limits. It has low irritation and comedogenic potential.

Research notes

The Cosmetic Ingredient Review (CIR) panel reviewed PEG stearates and concluded they are safe for use in cosmetics. Studies show low skin irritation and sensitization potential. No significant human health risks have been identified from topical use at typical concentrations.

Common label clues

Typical concentration: 1–5% in most leave-on products
Regulatory status: Approved for use in cosmetics by the U.S. FDA, EU CosIng, and Health Canada. The Cosmetic Ingredient Review (CIR) panel has deemed it safe as used in rinse-off and leave-on products.
Common uses: Moisturizers, Cleansers, Sunscreens, Makeup removers
Environmental note: PEG-100 Stearate is not readily biodegradable. It can persist in water systems, so eco-conscious consumers may prefer plant-based emulsifiers.

Good to know

PEG-100 Stearate is often paired with Glyceryl Stearate in a 1:1 ratio to create a self-emulsifying system.
The '100' refers to the polymer length, not a percentage — it's a naming convention for PEG compounds.

Common questions

What is PEG-100 Stearate in beauty products?

What does PEG-100 Stearate do in a beauty product?

Is PEG-100 Stearate safe for most people?

Who should be careful with PEG-100 Stearate?

Those with known sensitivity to PEG compounds People seeking fully natural or biodegradable formulations

Research sources

Cosmetic Ingredient Review (CIR) – Safety Assessment of PEG StearatesOpen European Chemicals Agency (ECHA) – PEG-100 StearateOpen PubMed – Skin compatibility of PEG emulsifiersOpen

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.