Cetrimonium Chloride

Cetrimonium chloride is a cationic quaternary ammonium surfactant/conditioning agent used in hair products (often ~0.1–2%), and this class is a well-recognized cause of stinging, irritant contact dermatitis, and eye/mucosal irritation when left on skin or used at higher exposures. Patch testing and clinical experience show it can provoke reactions in eczema-prone and barrier-impaired patients, so I score it as a notable irritant requiring caution, especially in leave-on or scalp products used frequently. Safety Notes: In consumer skincare/hair-adjacent products (e.g., cleansing creams, emulsified lotions, and rinse-off conditioners), cetrimonium chloride is most often used as a conditioning/antistatic cationic at very low levels around 0.05–0.3%, with some “cationic emulsifier” style systems landing ~0.5–1%. The highest OTC concentrations are seen in strong rinse-off hair conditioners, detanglers, and some antiseptic/cleansing products where regulatory limits allow up to ~2.5% in rinse-off; leave-on facial/body products are typically kept much lower (generally ≤0.5%) due to irritation/sensitization risk and EU Cosmetic Regulation constraints.