The ingredient, explained

Polymethylsilsesquioxane

A published expert assessment examines cosmetic-use safety.

Opacifying

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Ingredient guide

What it is and what it does

Polymer formed by hydrolysis and condensation of methyltrimethoxysilane

About this ingredient: EU CosIng ingredient registry (via Open Beauty Facts taxonomy) ↗

Opacifying: Makes a product less transparent.

Function definitions: European Commission ingredient function definitions (SCCNFP/0299/00, pages 16 to 20) ↗

Registry functions describe possible formulation roles, not results for a finished product. A dictionary entry is not an approval or a safety assessment.

A closer look

What the research shows

Safety assessment

The final report includes polymethylsilsesquioxane and supports the described cosmetic uses based on the available safety data.

What this does not tell us

The report discusses gaps in systemic-toxicity data and control of monomer impurities. A group safety conclusion is not proof of performance or individual tolerability.

Sources for this summary. Published source ↗

Research review checked Oct 1, 2026

Bounded targeted searches for the exact ingredient identity in primary research or final expert assessments, with selected-source verification. Not a systematic review.