Ingredient review

Butylaminoethyl Methacrylate Crosspolymer

INCI: Butylaminoethyl Methacrylate Crosspolymer

A synthetic polymer that helps makeup and skincare last longer by forming a flexible film on the skin, but it offers no active skincare benefits.

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In plain English

This is a plastic-like ingredient that creates a thin, flexible film on your skin or lashes. It's what makes waterproof mascara stay put and helps foundation resist smudging. Think of it as a clear, invisible shield that locks your makeup in place without feeling stiff or heavy.

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

Quick decision guide

Useful, but context matters

Butylaminoethyl Methacrylate Crosspolymer 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 Butylaminoethyl Methacrylate Crosspolymer.
  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 synthetic polymer made from methacrylate monomers, crosslinked to form a flexible, water-resistant film. It is commonly used in cosmetics to improve durability and texture.

How it works

When applied, the polymer molecules spread into a thin layer and then link together as the solvent evaporates, forming a continuous film. This film physically blocks water and oil from disturbing the product underneath, while also helping other ingredients adhere to the skin or lashes.

Pros

Excellent staying power

Creates a flexible film that keeps makeup in place for hours, even in humid or sweaty conditions.

Lightweight feel

Despite its strong hold, the film is thin and flexible, so it doesn't feel heavy or cakey on the skin.

Cons and cautions

No skincare benefit

This ingredient is purely functional—it doesn't hydrate, soothe, or treat the skin in any way.

Requires thorough removal

Because it's water-resistant, you'll need an oil-based cleanser or micellar water to fully remove it without rubbing.

Best for

  • Anyone wanting long-lasting, transfer-resistant makeup
  • People with oily skin who need extra staying power

Use caution if

  • Those who prefer minimal, water-based makeup routines

Usage tips

Use an oil-based cleanser or balm to remove products containing this polymer.
Layer it in setting sprays or primers for extra hold without adding thickness.

Safety summary

Considered safe for cosmetic use at typical concentrations. It is not absorbed into the skin and has a very low irritation and allergy potential. The main practical downside is that it requires a dedicated cleanser for removal.

Research notes

Safety assessments by the Cosmetic Ingredient Review (CIR) panel have concluded that methacrylate crosspolymers are safe in cosmetics when formulated properly. No significant human or environmental toxicity has been reported at use levels.

Common label clues

Typical concentration
0.5% to 5%
Regulatory status
Approved for use in cosmetics globally, including by the FDA (US) and EU CosIng database, with no known restrictions at typical concentrations.
Common uses
Mascara, Eyeliners, Long-wear foundations, Sunscreens, Setting sprays
Environmental note
As a synthetic polymer, it is not biodegradable. However, it is used in very small amounts and is removed during wastewater treatment.

Good to know

  • This polymer is often listed near the end of ingredient lists because it's used in small amounts.
  • It is not absorbed into the skin—it sits on the surface and washes off.

Common questions

What is Butylaminoethyl Methacrylate Crosspolymer in beauty products?

This is a plastic-like ingredient that creates a thin, flexible film on your skin or lashes. It's what makes waterproof mascara stay put and helps foundation resist smudging. Think of it as a clear, invisible shield that locks your makeup in place without feeling stiff or heavy.

What does Butylaminoethyl Methacrylate Crosspolymer do in a beauty product?

When applied, the polymer molecules spread into a thin layer and then link together as the solvent evaporates, forming a continuous film. This film physically blocks water and oil from disturbing the product underneath, while also helping other ingredients adhere to the skin or lashes.

Is Butylaminoethyl Methacrylate Crosspolymer safe for most people?

Considered safe for cosmetic use at typical concentrations. It is not absorbed into the skin and has a very low irritation and allergy potential. The main practical downside is that it requires a dedicated cleanser for removal.

Who should be careful with Butylaminoethyl Methacrylate Crosspolymer?

Those who prefer minimal, water-based makeup routines

Research sources

Cosmetic Ingredient Review (CIR) – Safety Assessment of Acrylate PolymersOpenPubChem – Butylaminoethyl MethacrylateOpenEU CosIng DatabaseOpen

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.