Po
Polyquaternium-51
Polyquaternium-51Hydrator
A film-forming polymer with a cell-membrane-like structure that locks moisture into the skin's surface.
What it does
Polyquaternium-51 is a water-soluble polymer. Its structure closely resembles the phospholipid layer found on cell surfaces. Applied to skin, it forms a thin film that helps prevent water loss. Research using laser scanning on real skin found it raised water levels in the outer skin layer. It is a moisturizing ingredient, not a traditional skin active.
The evidence, graded
moderateThe phosphorylcholine polymer pMPC (same class as Polyquaternium-51) raised water content in the outer skin layer both in lab tests and on real skin. The effect was measured with laser-based scanning that can read hydration without touching the skin.Chrit 2007 · Biopolymers ↗
Graded per the methodology: strong · moderate · emerging · expert consensus. A weak source on a strong claim gets the weaker label.
Also known as
phosphorylcholine polymer, pMPC
Pairs worth knowing
Browse all 668 ingredients — grouped by what they do, each with whatever evidence we can cite.
This page is public so a shared ingredient card always has its sources behind it — and so you can check them without an account.
Want more like this?
Every evidence-based flag cites its source, Drop tells you when your routine is complete, and it helps you simplify — instead of selling you more. The app launches on iOS and Android in October 2026. Rate my routine works today at /rate — no sign-in.