Polyquaternium-51
AKA “PQ-51, Polyquaternium-51”
Skin Conditioning
Ingredient Facts
Polyquaternium-51
AKA: PQ-51
Skin Conditioning · Film Forming · EWG: 1
Synthetic
Occlusive
Skin Conditioner
Clean
2-(N,N,N-Trimethylamino)ethyl 2-(2-methyl-2-propenoyloxy)ethyl phosphate inner salt, polymer with butyl 2-methyl-2-propenoate
CAS #
125275-25-4
Form
Powder
See origin →
Functions
Film Forming
Creates a physical seal on skin to lock moisture in and keep irritants out. The "slugging" ingredient — barrier protection.
Skin Conditioning
A catch-all term for ingredients that improve how skin looks and feels — softer, smoother, more supple. The workhorse behind most moisturizers.
Locks in moisture
Traditional Use
A synthetic quaternary ammonium polymer developed in the late 20th century for use as a conditioning and film-forming agent in hair and skincare products. Designed to replace natural conditioning agents and improve product texture and performance.
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
Verified Jun 2026
Data: CosIng · EWG · CIR