Cocamidopropyl betaine, also known by the acronym CAPB, is a sticky, yellow liquid derived from coconut oil and a chemical called dimethylaminopropylamine. It is a mild amphoteric surfactant — a detergent that can act as an acid or a base — and is typically used in bath and personal cleansing products. It helps produce foam in such products as bubble bath and can help thicken products such as hair conditioner. It also has mild antiseptic qualities. Allergic reactions and skin irritation are possible, especially for people with more sensitive skin.

Sometimes referred to as coco-betaine, cocamidopropyl betaine can also be labeled on product containers as N-(carboxy methyl)-N, N-dimethyl-3-[(1-oxococonut) amino]-1-propanaminium hydroxide, or inner salt. Cocamidopropyl betaine can be an effective foam booster or foam stabilizer, making it a common ingredient in bubble bath products, body washes and shampoos. It also can be used as a thickener or as an anti-static agent and is often found as an ingredient in hair conditioners. It has emulsifying and moisturizing capabilities as well and is commonly used in bath oils and cosmetics.

Cocamidopropyl betaine remains stable within a wide range of pH values. This pH range gives it a mild germicidal and antiseptic effect, making it suitable for use in personal sanitary products. For example, it often is included as a mild disinfectant ingredient in facial scrubs and exfoliants. It also is compatible with other cationic, anionic, and nonionic surfactants, making it a common ingredient such products as hair dye.

Though it is generally regarded as a mild and safe ingredient, there have been some cases of allergic reactions in users. This is most likely a result of the manufacturing byproducts amidoamine and dimethylaminopropylamine, two impurities that have been commonly associated with skin irritation and dermal allergies. Studies have shown that this problem can potentially be avoided if manufacturers keep the levels of these byproducts low.

In the past decade, more and more new surfactants have been introduced with the hopes of being milder and less irritating. The use of cocamidopropyl betaine has largely replaced the use of cocamide DEA in most products, due to studies that have shown possible carcinogenic effects on lab rats in the testing of cocamide DEA in cosmetics. Some hair and body cleanser manufacturers are now replacing cocamidopropyl betaine with cocamidopropyl hydroxysultaine, also derived from coconut oil, claiming that it is milder and more effective, though it tends to be a more expensive ingredient.