Cocamidopropyl betaine.

Cocamidopropyl betaine (CAPB) is an amphoteric synthetic detergent that has been increasingly used in cosmetics and personal hygiene products (eg, shampoos, contact lens solutions, toothpaste detergents, makeup removers, bath gels, skin care products, cleansers, liquid soaps, antiseptics, and gynecologic and anal hygiene products) because it induces relatively mild skin irritation. Delayed T-cell-mediated type IV hypersensitivity reactions to CAPB have been reported, and contact sensitization prevalence is estimated at between 3.0 and 7.2%. The increasing rates of sensitization led to CAPB's being named Allergen of the Year in 2004. Related impurities rendered during the manufacturing process (such as amidoamine and dimethylaminopropylamine) are thought to play a role in sensitization.