Polyisobutene
Plant-Derived Synthetic
Occlusive
Clean
Homopolymer of 2-methyl-1 propene
CAS #
9003-27-4
Functions
Binding
Film Forming
Creates a physical seal on skin to lock moisture in and keep irritants out. The "slugging" ingredient — barrier protection.
Viscosity Controlling
Strengthens Barrier
Antioxidant
Anti-Inflammatory
Creates protective layer
Holds ingredients together
Controls product thickness
Traditional Use
Developed as a petroleum-derived synthetic polymer in the mid-20th century. Introduced to cosmetics as a conditioning and film-forming agent to improve texture and wear properties of skincare and color cosmetics.
Skin Types
●all-skin-types, gentle
Best For
Dryness
Pregnancy & Breastfeeding Safe
Yes
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
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Verified Jun 2026
Data: CosIng · EWG · CIR