Polyisobutene

Polyisobutene 1
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Polyisobutene 2
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Plant-Derived Synthetic
Occlusive
Clean
OriginDerived from isobutylene, a hydrocarbon byproduct of petroleum refining and natural gas processing. Synthesized through catalytic polymerization of isobutylene monomers to create long-chain polymer chains.
Homopolymer of 2-methyl-1 propene
CAS #
9003-27-4
Skin Types
●all-skin-types, gentle
Best For
Dryness
Pregnancy & Breastfeeding Safe
Yes
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
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.
EWG
1
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not Comedogenic
Animal test found no comedogenicity in the CIR safety assessment (CIR 687)
Not a Skin Irritant
1 study / 1 not irritating (CIR 687)
Not a Sensitizer
1 study / 1 not sensitizing / plus 1 case report (CIR 455)
Mixed Eye Irritation Results
2 studies / 1 irritating / 1 not irritating / reactions slight (CIR 687)
Concentration Guide
Leave-on0.24–40%
Rinse-off1.1–3.5%
0%50%100%
CIR reported use · 2013 survey
Regulatory Status
USA✔ permitted
EU⚠ restricted
JAPAN⚠ restricted
CANADA⚠ restricted
Verified Jun 2026
Data: CosIng · EWG · CIR