Cocamidopropyl Betaine

Overview

Cocamidopropyl Betaine — often shortened to CAPB — is the most widely used amphoteric surfactant in commercial cosmetics. It shows up in almost every drugstore shampoo, every baby wash, every hand soap, every facial cleanser. If you read the back of a bottle and see something amphoteric, this is what it is nine times out of ten. It is supplied as a clear pale-yellow liquid, around 30% active.

The chemistry is a step more complicated than coco betaine. To make CAPB, coconut fatty acids are first reacted with dimethylaminopropylamine (DMAPA) to make cocamide, and then with chloroacetic acid to add the betaine group. The extra step gives a slightly more refined, more stable, slightly milder molecule than plain coco betaine — but it also leaves room for trace impurities (specifically DMAPA and amidoamine) that can occasionally irritate sensitive skin in lower-quality batches.

Like all amphoterics, CAPB carries both a positive and negative charge depending on pH. In acidic formulas it behaves cationic (slightly conditioning), in alkaline formulas it behaves anionic (slightly cleansing), and in the neutral middle it sits as a foam booster and irritation buffer.

What it does in a formula

Primary role: secondary surfactant, foam booster, and harshness reducer. CAPB is the classic partner for harsher anionic surfactants like SLES, SCS, and SCI — it softens the cleansing, improves the lather, and reduces stinging in eye-area products.

Secondary roles: viscosity builder (it noticeably thickens anionic systems, especially with a salt curve), foam stabilizer, and mild antistatic agent. It also gives the foam a noticeably creamier, denser feel compared to anionic-only systems.

How to use

CAPB comes as a liquid, typically 30% active. Confirm the spec on your bottle — the active percentage drives the active surfactant matter (ASM) math.

Add it to the water phase after the primary anionic surfactant has fully dissolved. No heat needed — but if your water phase is hot, wait until it drops below 70 C before adding CAPB to protect the molecule.

The classic ratio: 2:1 or 3:1 anionic-to-CAPB on an active basis. A face cleanser might be 6% SCI plus 2% CAPB active; a body wash 10% SLES plus 4% CAPB active.

Total formula percentage: 5-15% as supplied for most DIY shampoos and body washes (7-10% is the sweet spot). The broader allowed range runs 4-40%, so there is room to push higher in foam-heavy builds. CAPB itself sits at pH 5-6 in a 10% solution, which is one reason it slots into acidic skin-friendly formulas without fighting them.

Best for / Worst for

Best for: shampoos (regular and sulfate-free), body washes, hand soaps, baby cleansers, facial cleansers, micellar waters, no-tears formulas. Anywhere you need a mild, foam-boosting amphoteric to balance a harsher primary surfactant.

Worst for: people with documented CAPB sensitivities (it is a known sensitizer in a small percentage of users — coco betaine or sodium lauroamphoacetate is a better choice for those), ultra-clean-label products where the more complex synthesis is an issue, low-pH AHA cleansers below pH 3.

Common pitfalls

Biggest pitfall: assuming all CAPB is equal. The quality varies a lot between suppliers. Low-cost industrial-grade CAPB can have noticeable amidoamine impurities that cause contact dermatitis in sensitive users. Cosmetic-grade from a reputable supplier is worth the extra cost — established EU cosmetic-grade suppliers test for this.

Second: confusing supplied percentage with active percentage. A 10% CAPB label means 3% actual surfactant in the formula.

Third: storage. Like coco betaine, CAPB needs a tight cap and a clean dispensing tool. It can grow surface mold over time. The finished product still needs a broad-spectrum preservative.

Fourth: the CAPB-versus-coco-betaine debate. For most DIY purposes they are interchangeable. Use whichever you have on hand and adjust ratios on an active basis.

Substitutes

• Coco Betaine — almost identical, slightly more ‘natural’ label appeal, slightly higher impurity risk in low-grade batches. The most common direct swap.
• Sodium Lauroamphoacetate — milder, slightly less foam-boosting, better choice for very sensitive skin or eye-area cleansers.
• Disodium Cocoamphodiacetate — the gentlest of the amphoterics, used in premium baby washes, more expensive and harder to source.