Polyquaternium-51
Synthetic phosphorylcholine-based polymer that forms a moisturizing film. Human data are limited to one short study, and there are no data on use in pregnancy
Evidence by route
Topical application
Data exist only for moisturizing. In one small study, a single application of a 0.1% solution kept more water in the skin than water alone for up to 4 hours. Barrier repair has not been studied in people, and in laboratory work the polymer loosened stratum corneum lipids (Hu 2026). The claim of better water binding than hyaluronic acid has no source
- C
Moisturizing
The only human study used a single application of a 0.1% solution. The skin of 21 volunteers held more water for 4 hours than water-treated skin, and repeated use was not tested
- D
Barrier repair
Transepidermal water loss has not been measured in people; it fell only in four tape-stripped mice, and in laboratory work the polymer loosened stratum corneum lipids (Hu 2026)
- D
Holds water better than hyaluronic acid
No peer-reviewed study compares polyquaternium-51 with hyaluronic acid
- Hu Z et al. From Solubilization to Structural Perturbation: The Mechanism of Polyquaternium-51-Driven Enhanced Transdermal Delivery of Glabridin. Langmuir. 2026;42(26):18938-18952. PMID 42345215
- Kanekura T et al. Beneficial effects of synthetic phospholipid polymer, poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate), on stratum corneum function. Clin Exp Dermatol. 2002;27(3):230-4. PMID 12072015
How to read tiers A–F
- CWeak evidence. In vitro data, open-label studies, or expert consensus
- DNo data, or very weak or conflicting data
Tolerability and safety
- Working concentrations
- The only human study used a 0.1% water solution of the polymer, applied once; other concentrations have not been tested on human skin
- Irritation potential
- Low
- Allergen risk
- Low
- Pregnancy
- Unknown
- Suitable for
- Normal, Dry, Combination, Oily, Sensitive
About this ingredient
Polyquaternium-51 is a synthetic copolymer of 2-methacryloyloxyethyl phosphorylcholine (MPC) and butyl methacrylate, also known as PMB or poly(MPC-co-BMA) (Hu 2026). Its phosphorylcholine groups resemble the polar heads of cell membrane phospholipids. In skin care it works as a moisturizing film former. There is one study in people. In 21 healthy volunteers, a 0.1% water solution of the polymer was applied once to the forearm, with distilled water as the control (Kanekura 2002). Skin treated with the polymer held more water, measured by electrical conductance, at every point from 5 minutes to 4 hours. Randomization and blinding are not described, and repeated use was not studied. In the same paper the polymer lowered transepidermal water loss in four tape-stripped mice; in people this was not measured. In laboratory experiments and computer modeling, the polymer bound skin lipids, loosened the packing of stratum corneum lipids and helped glabridin penetrate deeper (Hu 2026). It may therefore change how other ingredients of a formula enter the skin. No published study compares its water binding with hyaluronic acid. There are no peer-reviewed data on irritation, sensitization or comedogenicity. There are no data on use during pregnancy or breastfeeding.
Frequently asked questions
Is Polyquaternium-51 safe during pregnancy?
Safety data for Polyquaternium-51 during pregnancy is insufficient. Best avoided when in doubt.
What skin types is Polyquaternium-51 for?
Polyquaternium-51 suits: normal, dry, combination, oily, sensitive.
What is Polyquaternium-51 and what does it do in cosmetics?
Synthetic phosphorylcholine-based polymer that forms a moisturizing film.
Is Polyquaternium-51 comedogenic?
On the Fulton scale 0/5 – non-comedogenic. For acne-prone skin, a rating of 3 or higher suggests choosing an alternative.
What's the INCI name for Polyquaternium-51?
The INCI name is Polyquaternium-51. It may also appear as: Lipidure.
What concentration of Polyquaternium-51 is effective?
The only human study used a 0.1% water solution of the polymer, applied once; other concentrations have not been tested on human skin
See Polyquaternium-51 in a product composition right on the store page
The Evigrade extension adds an evidence panel to iHerb, Sephora, Druni and 12 more stores. This ingredient and every other one in the product show evidence-tier, allergen risk and pregnancy/lactation flags at a glance.
Similar in action
Explore by category
Published: · updated: