Cocamidopropyl betaine (CAPB) is an amphoteric, synthetic detergent that has been increasingly used in cosmetics and personal hygiene products and induces a relatively mild skin irritation. This case evaluates allergic contact dermatitis developing due to CAPB. Allergy to CAPB was first reported in 1983. This case suffered from allergic contact dermatitis due to CAPB, which is a rare phenomenon despite widespread CAPB use.