Cocamidopropyl betaine is a gentle surfactant used in skin care products, mainly face and body washes, almost always used as a secondary cleansing agent, sometimes referred to as a co-surfactant. When used alone as the sole cleanser, it is generally too mild to cleanse adult skin and hair, but it is sometimes used as the sole cleanser in products for children. In any rinse-off formula, it also helps increase the lather or lather effect of cleansers.
Cocamidopropyl betaine can be plant-derived (most often from coconut) or synthetic, with both forms considered safe for use in cosmetic products. It is considered low risk for skin sensitization, although impurities from poor manufacturing—and not cocamidopropyl betaine itself—increase the risk, underscoring the importance of choosing well-formulated skin care products.
Cocamidopropyl betaine is approved for use up to 3% in leave-on products, but its concentration range for rinse-off formulas is much wider, typically between 4-40% depending on the properties of the formula. https://www.paulaschoice.com/ingredient-dictionary/ingredient-cocamidopropyl-betaine.html?q=Cocamidopropyl%20Betaine&fdid=ingredients