Cocamidopropyl betaine

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| Name = Lauramidopropyl betaine
| ImageFile = Cocamidopropyl betaine. svg
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| ImageSize = 244
| ImageName = Structural formula of lauramidopropyl betaine
| ImageCaption = Lauramidopropyl betaine, the major component of cocamidopropyl betaine
| IUPACName = {[3 (Dodecanoylamino)propyl](dimethyl)ammonio}acetate
| SystematicName =
| OtherNames = 2 [(3 Dodecanamidopropyl)dimethylaminio]acetate
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|Section2=Chembox Properties
| C=19 | H=38 | N=2 | O=3
| AtmosphericOHRateConstant =
| Appearance = Clear to slight yellow liquid
| BoilingPt notes=
| Density = 1.05 g/cm3
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| LogP =
| MeltingPt = <
| MeltingPtC = 10
| MeltingPt ref = CAPB is available as a viscous pale yellow solution and it is used as a surfactant in personal care products and animal husbandry. The name reflects that the major part of the molecule, the lauric acid group, is derived from coconut oil. Cocamidopropyl betaine to a significant degree has replaced cocamide DEA.

CAPB is a fatty acid amide containing a long hydrocarbon chain at one end and a polar group at the other. This allows CAPB to act as a surfactant and as a detergent. It is a zwitterion, consisting of both a quaternary ammonium cation and a carboxylate.

Cocamidopropyl betaine is used as a foam booster in shampoos. It is a medium strength surfactant also used in bath products like hand soaps. It is also used in cosmetics as an emulsifying agent and thickener, and to reduce irritation purely ionic surfactants would cause. It also serves as an antistatic agent in hair conditioners, which most often does not irritate skin or mucous membranes. However, some studies indicate it is an allergen. CAPB, as an additive, helps to scale up the gas hydrates' formation process.

CAPB has been claimed to cause allergic reactions in some users, but a controlled pilot study has found that these cases may represent irritant reactions rather than true allergic reactions. Furthermore, results of human studies have shown that CAPB has a low sensitizing potential if impurities with amidoamine (AA) and dimethylaminopropylamine (DMAPA) are low and tightly controlled. Other studies have concluded that most apparent allergic reactions to CAPB are more likely due to amidoamine. Cocamidopropyl betaine was voted 2004 Allergen of the Year by the American Contact Dermatitis Society.