Ingredient review

Castor Oil/IPDI Copolymer

INCI: CASTOR OIL/IPDI COPOLYMER

A semi-synthetic film-former that helps makeup and skincare stay put longer, but may feel heavy on some skin types.

beautyskincarefilm-former

In plain English

Castor Oil/IPDI Copolymer is a plastic-like ingredient made by combining castor oil with a synthetic compound called isophorone diisocyanate. In your cosmetics, it creates a thin, flexible film on your skin or lashes that helps the product resist water, sweat, and smudging. Think of it as a gentle glue that keeps your makeup in place without being sticky.

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

Castor Oil/IPDI 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/IPDI 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

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 polymer created by reacting castor oil (a natural vegetable oil) with isophorone diisocyanate (a synthetic building block). The result is a flexible, water-resistant film-former commonly used in long-wear and waterproof cosmetics.

How it works

When applied, the copolymer molecules link together to form a continuous, invisible film over the skin or hair. This film physically blocks water and oil from breaking down the product, while also helping pigments and other ingredients stay evenly distributed. It also slightly thickens the formula, giving it a richer texture.

Pros

Excellent staying power

Creates a durable film that helps makeup resist sweat, humidity, and water, so you don't have to touch up as often.

Flexible feel

Unlike some stiff film-formers, this copolymer forms a flexible layer that moves with your skin, reducing cracking or flaking.

Cons and cautions

Can feel heavy

On dry or sensitive skin, the film may feel tight or mask-like, especially in high concentrations.

Removal requires effort

Because it's water-resistant, you'll likely need an oil-based or dual-phase makeup remover to fully cleanse it away.

Best for

People who want long-wearing, waterproof makeup
Those with normal to oily skin who need extra staying power

Use caution if

Individuals with very dry or dehydrated skin who prefer lightweight, breathable formulas
Anyone sensitive to synthetic polymers or who prefers fully natural products

Usage tips

Use an oil-based cleanser or micellar water to thoroughly remove products containing this copolymer.

If you have dry skin, pair with a hydrating primer or moisturizer underneath to prevent a tight feeling.

Shake well before using if the product contains this ingredient, as it can settle over time.

Safety summary

Castor Oil/IPDI Copolymer is considered safe for cosmetic use at typical concentrations. The isophorone diisocyanate is fully reacted during manufacturing, so it does not remain in a free form that could cause irritation. However, individuals with known sensitivities to synthetic polymers should patch-test first.

Research notes

Limited independent studies exist specifically on this copolymer, but it is structurally similar to other polyurethane film-formers that have been evaluated for safety. The Cosmetic Ingredient Review (CIR) panel has assessed related polymers and found them safe when formulated properly.

Common label clues

Typical concentration: 1–10% in leave-on formulas
Regulatory status: Approved for use in cosmetics in the EU, USA, and many other regions. The isophorone diisocyanate component is tightly regulated to ensure it is fully reacted and safe in the final product.
Common uses: Long-wear foundations, Waterproof mascaras, Lip products, Sunscreens
Environmental note: As a synthetic polymer, this ingredient is not readily biodegradable. It may contribute to microplastic pollution if washed into waterways. Some brands are moving toward more eco-friendly alternatives.

Good to know

This ingredient is often listed near the end of an INCI list because it's used at low concentrations.
It is not the same as pure castor oil — the copolymer has very different properties and is not moisturizing.

Common questions

What is Castor Oil/IPDI Copolymer in beauty products?

What does Castor Oil/IPDI Copolymer do in a beauty product?

Is Castor Oil/IPDI Copolymer safe for most people?

Who should be careful with Castor Oil/IPDI Copolymer?

Individuals with very dry or dehydrated skin who prefer lightweight, breathable formulas Anyone sensitive to synthetic polymers or who prefers fully natural products

Research sources

Cosmetic Ingredient Review (CIR) – Safety Assessment of Polyurethane PolymersOpen European Chemicals Agency (ECHA) – Isophorone Diisocyanate InformationOpen PubMed – Film-Forming Polymers in CosmeticsOpen

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.