What it is
Polyquaternium-37 is a cross-linked quaternary ammonium polymer derived from a methacrylate monomer, carrying a positive charge that lets it bind to skin and hair surfaces. In sunscreens and emulsions it is used mainly to build viscosity, stabilize the emulsion, and improve the sensory feel of the product. It is frequently supplied as a pre-neutralized dispersion in an emollient carrier, which allows cold processing and rapid thickening.
Safety & warnings
Polyquaternium-37 is a large polymer that is not appreciably absorbed through intact skin and is generally well tolerated in cosmetic use. It is not a recognized fragrance allergen and is not a comedogenic oil. As with any rheology polymer, the carrier solvent or emulsifier it is supplied in, rather than the polymer itself, is the more likely source of any irritation.
Origin & sourcing
Synthetic; manufactured by polymerizing quaternized methacrylate monomers, typically supplied as a liquid dispersion in an oil or ester carrier.
Questions everyone asks
What does Polyquaternium-37 do in a sunscreen?
It thickens and stabilizes the formula, helping suspend the other ingredients and giving the product a smoother, more uniform texture.
Is Polyquaternium-37 the same as a silicone?
No. It is a cationic acrylate polymer, not a silicone, although both are sometimes used to improve the feel of a product.