Nonoxynol-6 is a nonylphenol ethoxylate derivative. Nonylphenol ethoxylates represent a group of synthetic, non-ionic surfactants derived from nonylphenols. They differ from one another in the number of hydrophilic ethoxy units of the polyethylene glycol side chain. The number of ethoxy units is declared in the name e.g. nonoxynol-6 with 6 ethoxy units.
Nonoxynol-6 is used in cosmetic formulations. The substance acts as emulsifier (changes the interfacial tension of liquids like water and oil so that they can be mixed together) and as surfactant (washing-active substance).