murphyPolymethylsilsesquioxane
AKA: Methyl Silsesquioxane, Resin Silicate
Synthetic
Clean
OriginDerived from silicon-based polymers in the silsesquioxane chemical family synthesized from silicone precursors. Produced through hydrolytic condensation and polymerization of methyltrimethoxysilane or similar organosilicon monomers.
Polymer formed by hydrolysis and condensation of methyltrimethoxysilane
CAS #
68554-70-1
Form
Liquid
Skin Types
●all-skin-types, gentle
Best For
General
Pregnancy & Breastfeeding Safe
Yes
Functions
Opacifying
Adds Opacity
Creates creamy opacity
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 Phototoxic
Product formulation test found no phototoxicity in the CIR safety assessment (CIR 743)
Not a Sensitizer
4 studies / 4 not sensitizing (CIR 743)
Not an Eye Irritant
1 study / 1 not irritating (CIR 743)
Mixed Skin Irritation Results
2 studies / 1 irritating / 1 not irritating / reactions slight (CIR 743)
Concentration Guide
Leave-on0.00001–55.2%
Rinse-off0.01–7.5%
0%50%100%
CIR reported use · report published 2017
Regulatory Agencies
Verified Jun 2026
Data: CosIng · EWG · CIR