C11-15sec-pareth (inci)

The polyoxyethylene ethers of synthetic fatty alcohols are called "pareth" (for comparison see: laurethe as polyoxyethylene ether of lauryl alcohol; steareth as polyoxyethylene ether of stearyl alcohol, etc.).

Polyalkylene glycol ethers are non-ionic surfactants whose lipophilic part consists of fatty alcohols (e.g. lauryl alcohol, palmitic alcohol, stearyl alcohols etc.). The hydrophilic part is formed by short-chain polyethylene glycols (polyoxyethylene). In the designation of fatty alcohol polyglycol ethers, the inserted numbering means the average number of ethylene oxide units per mole. The C numbering (e.g. C11-15) designates a synthetic C11-C15 fatty alcohol.

Thus, the INCI designation C11-15 Pareth defines a synthetic fatty alcohol containing C11-C15 C-atoms which is used in cosmetic products as surfactant and emulsifier.