Ingredient review
PEG-40 Isostearate
INCI: PEG-40 Isostearate
A reliable emulsifier that helps create stable, creamy formulas without common irritation.
In plain English
PEG-40 Isostearate is a synthetic ingredient that acts like a bridge between water and oil. In a lotion or cleanser, it stops the formula from separating into watery and oily layers. It is made by attaching 40 units of polyethylene glycol to isostearic acid (a fatty acid), which gives it both water-loving and oil-loving properties. This makes it especially useful in rinse-off products like makeup removers and gentle cleansers.
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-40 Isostearate 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-40 Isostearate.
- 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 polyethylene glycol derivative of isostearic acid, used as a non-ionic emulsifier and surfactant in cosmetics.
How it works
It reduces surface tension between oil and water, allowing them to mix into a stable emulsion. In cleansers, it helps lift and disperse oils and makeup so they can be rinsed away easily.
Pros
Effective emulsifier
Helps oil and water blend smoothly, preventing separation and ensuring a consistent texture in creams and cleansers.
Low irritation potential
Generally well-tolerated in rinse-off products, making it suitable for sensitive skin types when used as directed.
Cons and cautions
Potential trace impurity
Manufacturing can produce trace amounts of 1,4-dioxane, a possible carcinogen, though levels are tightly regulated in many regions.
Not ideal for all leave-on products
May feel slightly tacky or heavy on very oily skin if used in high concentrations in leave-on formulations.
Best for
- People who use creamy cleansers or makeup removers
- Those with normal to dry skin looking for gentle cleansing
Use caution if
- Individuals with known sensitivity to PEG compounds (rare)
Usage tips
Safety summary
PEG-40 Isostearate is considered safe for use in cosmetics at typical concentrations. The main safety concern is potential contamination with 1,4-dioxane, which is regulated. For most people, it is non-irritating and non-comedogenic in rinse-off products.
Research notes
Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that PEG compounds are safe as used in cosmetics when manufactured to purity standards. No significant skin sensitization or irritation has been reported for PEG-40 Isostearate specifically.
Common label clues
- Typical concentration
- 0.5% to 5%
- Regulatory status
- Approved for use in cosmetics in the EU, US, and many other countries. Manufacturers are required to limit 1,4-dioxane impurities to safe levels (e.g., under 10 ppm in the EU).
- Common uses
- Cleansers, Lotions, Creams, Makeup removers
- Environmental note
- PEG compounds are synthetic and not readily biodegradable, but they are used in low concentrations and are generally considered low risk in aquatic environments.
Good to know
- PEG-40 Isostearate is often found in micellar waters and oil cleansers.
- The '40' refers to the number of ethylene glycol units, which affects its water solubility.
Common questions
What is PEG-40 Isostearate in beauty products?
PEG-40 Isostearate is a synthetic ingredient that acts like a bridge between water and oil. In a lotion or cleanser, it stops the formula from separating into watery and oily layers. It is made by attaching 40 units of polyethylene glycol to isostearic acid (a fatty acid), which gives it both water-loving and oil-loving properties. This makes it especially useful in rinse-off products like makeup removers and gentle cleansers.
What does PEG-40 Isostearate do in a beauty product?
It reduces surface tension between oil and water, allowing them to mix into a stable emulsion. In cleansers, it helps lift and disperse oils and makeup so they can be rinsed away easily.
Is PEG-40 Isostearate safe for most people?
PEG-40 Isostearate is considered safe for use in cosmetics at typical concentrations. The main safety concern is potential contamination with 1,4-dioxane, which is regulated. For most people, it is non-irritating and non-comedogenic in rinse-off products.
Who should be careful with PEG-40 Isostearate?
Individuals with known sensitivity to PEG compounds (rare)
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.