PEG-100 stearate is a waxy, water-soluble emulsifier used in lotions, creams, and other skincare products to blend oil and water into a stable, smooth mixture. It’s made by combining stearic acid (a fatty acid found naturally in coconut or palm oil) with polyethylene glycol, a process that links about 100 units of ethylene oxide to the fat molecule. That “100” in the name refers to those ethylene oxide units, which make the ingredient highly water-loving and effective at keeping formulas from separating.
How It Works in Skincare Products
Oil and water don’t mix on their own. PEG-100 stearate sits at the boundary between oil droplets and the surrounding water in a formula, lowering the surface tension so the two phases stay evenly blended rather than splitting apart. It’s classified as a nonionic emulsifier, meaning it carries no electrical charge. This makes it gentler and less reactive than charged surfactants, which is one reason it shows up so frequently in facial moisturizers and body lotions.
Beyond holding a formula together, PEG-100 stearate also acts as a mild emollient. It helps skin feel soft by forming a light layer that traps moisture. The ingredient contributes to product texture as well, giving creams a smooth, even consistency that spreads easily without feeling greasy.
Why It’s Often Paired With Glyceryl Stearate
If you’ve checked an ingredient list and spotted PEG-100 stearate, there’s a good chance glyceryl stearate appears right next to it. The two are frequently sold as a pre-blended emulsifier system because they work better together than either does alone. Glyceryl stearate is a lipid-friendly co-emulsifier that stabilizes the oil side of the mixture while PEG-100 stearate handles the water side.
This combination creates oil-in-water emulsions that are notably stable and pleasant to use. Products made with this blend tend to feel lighter and fluffier than those made with traditional emulsifying wax, with less of a waxy residue on the skin. When formulators add fatty alcohols and thickeners to the mix, the same blend can produce richer, more buttery textures like those found in body butters. That versatility is a big part of its appeal for cosmetic chemists.
Where the Stearic Acid Comes From
The stearic acid in PEG-100 stearate generally comes from either palm oil or coconut oil. This means the ingredient may raise concerns for people who avoid palm-derived products for environmental reasons. Some manufacturers offer versions sourced exclusively from coconut, though this isn’t always disclosed on the label. The source of the stearic acid also determines whether the ingredient qualifies as vegan or halal, since stearic acid can technically come from animal fats as well. If this matters to you, checking with the brand directly is the most reliable way to confirm the source.
Safety and Skin Compatibility
PEG-100 stearate has a comedogenicity rating of 0, meaning it is not expected to clog pores. Its irritancy rating is also 0. These ratings make it a reasonable choice for most skin types, including oily and acne-prone skin, at least from a pore-clogging standpoint.
PEG-based compounds as a group have been reviewed for cosmetic safety. Related PEGylated oils evaluated in a safety review published in Toxicological Research were found to be generally non-irritating and non-sensitizing to human skin, even at high concentrations. Regulatory bodies have concluded these compounds are safe for use in cosmetics. That said, one caveat worth knowing: some skincare communities flag PEG-100 stearate as a potential concern for fungal acne (malassezia folliculitis), since the fatty acid component could theoretically feed the yeast involved. If you’re prone to fungal breakouts on your chest, back, or forehead, this is worth keeping in mind.
The 1,4-Dioxane Question
Any ingredient with “PEG” in its name can contain trace amounts of a contaminant called 1,4-dioxane, a byproduct of the manufacturing process. This isn’t added intentionally, and the amounts are extremely small. The FDA identifies ingredients with the prefixes “PEG,” “polyethylene,” or “polyoxyethylene” as categories where this contaminant can form. Europe’s Scientific Committee on Consumer Safety has concluded that levels at or below 10 parts per million in finished cosmetic products are safe for consumers. Reputable manufacturers use purification steps (typically vacuum stripping) to reduce these traces well below that threshold. The presence of 1,4-dioxane is a manufacturing quality issue rather than an inherent danger of the ingredient itself.
Common Product Types
You’ll find PEG-100 stearate in a wide range of products:
- Facial moisturizers and serums where a lightweight, non-greasy texture is important
- Body lotions and creams that need to spread easily over large areas
- Body butters when blended with fatty alcohols for a thicker consistency
- Sunscreens that combine mineral or chemical UV filters with a water-based formula
- Hair conditioners where oil-phase conditioning agents need to be evenly distributed
It typically appears in concentrations between 1% and 5% of a formula, placing it in the middle or lower half of most ingredient lists. At these levels it functions purely as a structural ingredient, holding the product together rather than delivering active skincare benefits on its own.