Ingredient review
Castor Oil Dimer Copolymer
INCI: Bis-Isostearoyl Castor Oil/Dimer Dilinoleate Copolymer
A gentle film-forming polymer that improves wear and texture without common irritation risks.
In plain English
This ingredient is a modified castor oil molecule that forms a thin, flexible film on your skin or hair. It helps makeup last longer, keeps sunscreen from rubbing off easily, and gives products a smooth, non-greasy feel. Because it's derived from castor oil, it's generally well-tolerated and unlikely to clog pores or cause irritation.
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
- semi synthetic
- Evidence
- moderate
- Irritation
- low
- Clogging risk
- low
Quick decision guide
Useful, but context matters
Castor Oil Dimer Copolymer 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 Castor Oil Dimer Copolymer.
- 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 semi-synthetic polymer created by chemically bonding castor oil derivatives with dimer dilinoleic acid. It functions as a film former and viscosity modifier in cosmetics.
How it works
When applied, the polymer molecules link together to create a continuous, flexible film on the skin or hair surface. This film helps other ingredients stay in place, improves water resistance, and gives a smooth, even finish.
Pros
Long-lasting wear
Helps makeup and sunscreen stay put for hours without smudging or fading.
Gentle on skin
Derived from castor oil, it has a low irritation and comedogenic risk, making it suitable for most skin types.
Cons and cautions
Potential tackiness
In high concentrations, it can leave a slightly sticky or heavy feel on the skin.
Limited absorption data
There is not much research on how much of this polymer penetrates the skin or its long-term effects.
Best for
- Anyone seeking long-wear makeup or sunscreen
- People with normal to oily skin who want a matte finish
Use caution if
- Those with extremely sensitive skin who prefer minimal ingredient lists
Usage tips
Safety summary
Generally recognized as safe for topical use. Low irritation and comedogenic potential. No significant safety concerns reported in cosmetic concentrations.
Research notes
Limited peer-reviewed studies specifically on this polymer, but it is structurally similar to other safe film-forming agents. Safety is supported by its widespread use and low reported adverse effects.
Common label clues
- Typical concentration
- 1% to 10%
- Regulatory status
- Approved for use in cosmetics in the US, EU, and other major markets. No specific restrictions noted.
- Common uses
- Mascara, Lip products, Sunscreens, Long-wear foundations
- Environmental note
- Derived from renewable castor oil, but the chemical modification process may have some environmental impact.
Good to know
- This ingredient is often used in 'transfer-proof' lipsticks and eyeliners.
- It is considered biodegradable due to its castor oil base.
Common questions
What is Castor Oil Dimer Copolymer in beauty products?
This ingredient is a modified castor oil molecule that forms a thin, flexible film on your skin or hair. It helps makeup last longer, keeps sunscreen from rubbing off easily, and gives products a smooth, non-greasy feel. Because it's derived from castor oil, it's generally well-tolerated and unlikely to clog pores or cause irritation.
What does Castor Oil Dimer Copolymer do in a beauty product?
When applied, the polymer molecules link together to create a continuous, flexible film on the skin or hair surface. This film helps other ingredients stay in place, improves water resistance, and gives a smooth, even finish.
Is Castor Oil Dimer Copolymer safe for most people?
Generally recognized as safe for topical use. Low irritation and comedogenic potential. No significant safety concerns reported in cosmetic concentrations.
Who should be careful with Castor Oil Dimer Copolymer?
Those with extremely sensitive skin who prefer minimal ingredient lists
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.