Polymethylsilsesquioxane

Polymethylsilsesquioxane 1
AKA: Methyl Silsesquioxane, Resin Silicate
Synthetic
Silicone
Clean
Polymer formed by hydrolysis and condensation of methyltrimethoxysilane
CAS #
68554-70-1
Form
Liquid
Functions
Opacifying
Adds Opacity
Creates creamy opacity
Traditional Use
Developed in the late 20th century as a silicone-based polymer. Used in modern cosmetics as a lightweight texture enhancer and mattifying agent, particularly in powders and liquid foundations.
EWG
1
CIR
Safe as used
Pregnancy
Yes
CIR Safety Findings
Not a Sensitizer
ewg-1
medical-approval
pregnancy-nursing-safe
all-shades-safe
Regulatory Status
USA✔ permitted
EU⚠ restricted
JAPAN⚠ restricted
CANADA⚠ restricted
Skin Types
●all-skin-types, gentle
Best For
General
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.
Verified Jun 2026
Data: CosIng · EWG · CIR