What it is
Carbomer is a large polymer built from repeated subunits of acrylic acid, supplied as a white, fluffy powder. In water it behaves as an anionic polyelectrolyte whose chains absorb large amounts of water and swell, which lets it thicken liquids and form gels. To activate this gelling it usually has to be neutralized with a base, such as sodium hydroxide, after which it creates viscous, clear gels that feel smooth and non-tacky on the skin. It is typically used at low levels, around 1 percent or less, and also helps stabilize emulsions.
Safety & warnings
Carbomer is a high-molecular-weight polymer that stays on the skin surface and is used at low concentrations purely to control texture, so it is generally well tolerated. Because it must be neutralized to a skin-friendly pH to gel properly, finished products are formulated to avoid the acidity of the raw polymer. It is a common, long-established thickener with a well-characterized formulation role.
Origin & sourcing
Carbomer is synthetic, made by polymerizing acrylic acid together with a cross-linking agent and then neutralizing most of the carboxyl groups, commonly with sodium hydroxide. The dry polymer is a white powder that is dispersed in water and neutralized in the formula to develop its gel structure.