Ingredient review
PEG-66 Trihydroxystearin
INCI: PEG-66 Trihydroxystearin
A reliable synthetic emulsifier that helps keep your creams and lotions smooth and stable, with a low risk of irritation.
In plain English
PEG-66 Trihydroxystearin is a man-made ingredient that acts like a bridge between water and oil in your skincare products. Without it, the water and oil in a cream or lotion would separate, just like salad dressing does. It keeps the formula smooth, consistent, and easy to apply. The 'PEG' part means it's made with polyethylene glycol, a common building block in cosmetics that also helps the ingredient dissolve nicely.
Review score
Safety, usefulness, and evidence
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
Quick decision guide
Useful, but context matters
PEG-66 Trihydroxystearin 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-66 Trihydroxystearin.
- 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
lowLess likely to sting, burn, or bother most users, though sensitive skin can still react.
Clogging risk
lowLess likely to feel heavy or contribute to clogged pores for most skin types.
Evidence level
moderateThere is useful support, but formula details and claim strength still matter.
What it is
A synthetic polymer derived from castor oil and polyethylene glycol, used primarily as an emulsifier and stabilizer in cosmetic formulations.
How it works
It reduces the surface tension between water and oil molecules, allowing them to mix into a stable, uniform emulsion. This prevents separation and gives creams and lotions their smooth, spreadable texture.
Pros
Excellent emulsifier
Effectively blends water and oil, preventing your cream from separating and ensuring a consistent texture every time you use it.
Low irritation risk
Rated as low-irritation and low-comedogenic, making it a safe choice for most skin types, including sensitive skin.
Cons and cautions
Synthetic origin
It is a man-made ingredient, which may be a turn-off for those seeking fully natural or clean beauty products.
Potential purity concerns
Like all PEG compounds, manufacturing impurities such as ethylene oxide are possible, but reputable suppliers follow strict purification processes.
Best for
- Anyone using water-and-oil based creams or lotions
- People with normal to dry skin looking for stable, well-formulated moisturizers
Use caution if
- Those who strictly avoid all synthetic or PEG-based ingredients
Usage tips
Safety summary
PEG-66 Trihydroxystearin is considered safe for use in cosmetics at typical concentrations. It has low irritation and comedogenic potential, making it suitable for most skin types. As with all PEGs, quality control is important to avoid impurities.
Research notes
The Cosmetic Ingredient Review (CIR) panel has evaluated PEG compounds and found them safe for use in cosmetics. Specific studies on PEG-66 Trihydroxystearin are limited, but its chemical class is well-understood and widely used.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics by the FDA and the European Commission, with no concentration restrictions in leave-on or rinse-off products.
- Common uses
- Moisturizers, Sunscreens, Foundations, Creams and lotions
- Environmental note
- As a synthetic polymer, it is not biodegradable. However, it is used in very small amounts and is not known to accumulate in the environment.
Good to know
- PEG-66 Trihydroxystearin is often used in sunscreens to help distribute UV filters evenly.
- It is considered safe by major regulatory bodies when used in cosmetic concentrations.
Common questions
What is PEG-66 Trihydroxystearin in beauty products?
PEG-66 Trihydroxystearin is a man-made ingredient that acts like a bridge between water and oil in your skincare products. Without it, the water and oil in a cream or lotion would separate, just like salad dressing does. It keeps the formula smooth, consistent, and easy to apply. The 'PEG' part means it's made with polyethylene glycol, a common building block in cosmetics that also helps the ingredient dissolve nicely.
What does PEG-66 Trihydroxystearin do in a beauty product?
It reduces the surface tension between water and oil molecules, allowing them to mix into a stable, uniform emulsion. This prevents separation and gives creams and lotions their smooth, spreadable texture.
Is PEG-66 Trihydroxystearin safe for most people?
PEG-66 Trihydroxystearin is considered safe for use in cosmetics at typical concentrations. It has low irritation and comedogenic potential, making it suitable for most skin types. As with all PEGs, quality control is important to avoid impurities.
Who should be careful with PEG-66 Trihydroxystearin?
Those who strictly avoid all synthetic or PEG-based ingredients
Research sources
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.