Ingredient review

PEG-40 Hydrogenated Castor Oil Isostearate

INCI: PEG-40 HYDROGENATED CASTOR OIL ISOSTEARATE

A gentle emulsifier that helps mix oil and water in your skincare, but may feel heavy on very oily or acne-prone skin.

beautyskincareemulsifier

In plain English

PEG-40 Hydrogenated Castor Oil Isostearate is a helper ingredient that allows water and oil to blend together smoothly in products like cleansers and creams. It is made by treating castor oil with a process called ethoxylation (adding PEG chains) and then reacting it with isostearic acid. This makes it a mild surfactant that can also thicken formulas. While generally safe and non-irritating, it can leave a slightly greasy feel on some skin types.

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
semi synthetic
Evidence
moderate
Irritation
low
Clogging risk
low
How reviews are scored

Quick decision guide

Useful, but context matters

PEG-40 Hydrogenated Castor Oil 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.

  1. Step 1Start with the score, then check the irritation and clogging risk before judging PEG-40 Hydrogenated Castor Oil Isostearate.
  2. Step 2Use the "Best for" and "Use caution if" sections to match the ingredient to your skin, not just to a marketing claim.
  3. 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

A semi-synthetic emulsifier created by chemically modifying hydrogenated castor oil with polyethylene glycol (PEG) and isostearic acid. It is a waxy solid at room temperature and is used to stabilize oil-in-water emulsions.

How it works

It reduces the surface tension between oil and water, allowing them to mix into a stable, uniform cream or lotion. It also helps disperse other ingredients evenly and can boost the cleansing power of a formula by trapping dirt and oil.

Pros

Effective emulsifier

Helps create stable, smooth creams and lotions that don't separate, ensuring a consistent texture and feel every time you use the product.

Gentle on skin

Has a low irritation profile, making it suitable for sensitive skin types that react to harsher surfactants like sodium lauryl sulfate.

Cons and cautions

Potential for greasiness

On oily or acne-prone skin, this ingredient can leave a residual film that feels heavy or may contribute to clogged pores over time.

Ethoxylation concerns

The manufacturing process can generate trace amounts of 1,4-dioxane, a possible carcinogen, though reputable brands purify their ingredients to meet safety limits.

Best for

  • People with dry or normal skin who use rich creams or oil-based cleansers
  • Those looking for a gentle, non-stripping makeup remover

Use caution if

  • Individuals with very oily or acne-prone skin may find it too heavy or pore-clogging

Usage tips

Use in rinse-off products like cleansers or makeup removers to minimize any heavy feel on the skin.
If you have oily skin, look for formulas where this ingredient appears lower on the ingredient list (after water and main actives).

Safety summary

Generally recognized as safe for cosmetic use with low irritation and comedogenic potential. The main concern is trace 1,4-dioxane contamination, but reputable manufacturers purify their ingredients to meet safety standards. Overall, it is a well-tolerated emulsifier for most skin types.

Research notes

The Cosmetic Ingredient Review (CIR) panel reviewed PEG-40 Hydrogenated Castor Oil Isostearate and related compounds, concluding they are safe in current cosmetic practices. Studies show low acute toxicity and minimal skin irritation. No significant human or animal data suggest long-term health risks at typical exposure levels.

Common label clues

Typical concentration
1–5% in most leave-on and rinse-off products
Regulatory status
Approved for use in cosmetics in the US, EU, and many other regions. The Cosmetic Ingredient Review (CIR) panel has deemed it safe as used in rinse-off and leave-on products.
Common uses
Cleansers, Makeup removers, Lotions, Creams
Environmental note
As a semi-synthetic ingredient, it is not readily biodegradable in all environments, but it is not classified as a major environmental concern at typical usage levels.

Good to know

  • PEG-40 Hydrogenated Castor Oil Isostearate is often used in micellar waters and cleansing balms for its ability to dissolve makeup without harsh rubbing.
  • It is considered safe by the Cosmetic Ingredient Review (CIR) panel at concentrations up to 100%, though typical use is much lower.

Common questions

What is PEG-40 Hydrogenated Castor Oil Isostearate in beauty products?

PEG-40 Hydrogenated Castor Oil Isostearate is a helper ingredient that allows water and oil to blend together smoothly in products like cleansers and creams. It is made by treating castor oil with a process called ethoxylation (adding PEG chains) and then reacting it with isostearic acid. This makes it a mild surfactant that can also thicken formulas. While generally safe and non-irritating, it can leave a slightly greasy feel on some skin types.

What does PEG-40 Hydrogenated Castor Oil Isostearate do in a beauty product?

It reduces the surface tension between oil and water, allowing them to mix into a stable, uniform cream or lotion. It also helps disperse other ingredients evenly and can boost the cleansing power of a formula by trapping dirt and oil.

Is PEG-40 Hydrogenated Castor Oil Isostearate safe for most people?

Generally recognized as safe for cosmetic use with low irritation and comedogenic potential. The main concern is trace 1,4-dioxane contamination, but reputable manufacturers purify their ingredients to meet safety standards. Overall, it is a well-tolerated emulsifier for most skin types.

Who should be careful with PEG-40 Hydrogenated Castor Oil Isostearate?

Individuals with very oily or acne-prone skin may find it too heavy or pore-clogging

Research sources

Cosmetic Ingredient Review (CIR) – Safety Assessment of PEGsOpenPubChem – PEG-40 Hydrogenated Castor Oil IsostearateOpenEuropean Chemicals Agency (ECHA) – Substance InformationOpen

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.