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Surfactants & Emulsifiers

Cocamidopropyl Betaine

Also known as: CAPB, Coco betaine, CAPB surfactant

The foam-boosting co-surfactant from coconut — gentle enough for baby shampoo, with an allergy reputation built on impurities.

  • By IngredientWiki Editorial Team
  • Fact-checked by IngredientWiki Editorial Team
  • Updated 2026-09-26
  • 2 min read

In short

Cocamidopropyl betaine (CAPB) is a mild amphoteric surfactant derived from coconut oil, used to boost foam and soften harsh cleansers in shampoos, body washes, and baby products. Its gentleness is real — it is a standard choice in 'tear-free' formulas precisely because it is among the least irritating surfactants — but it also held the American Contact Dermatitis Society's 'allergen of the year' title in 2004. The twist: most CAPB allergy turned out to be caused by manufacturing impurities (amidoamine and DMAPA) rather than CAPB itself; modern high-purity grades have very low sensitization rates. It remains one of the most useful and well-characterized surfactants in personal care.

  • Amphoteric surfactant derived from coconut oil
  • Foam booster and mildness agent in shampoos/body wash
  • 2004 'allergen of the year' — mostly due to impurities
  • High-purity modern grades: very low sensitization

What is Cocamidopropyl Betaine?

Cocamidopropyl betaine does the invisible work of the shower: it turns thin, harsh detergent solutions into rich, creamy, gentle foam. Almost every shampoo, body wash, and 'tear-free' baby cleanser relies on it — usually paired with sulfates or their alternatives — to soften cleansing while boosting lather. Its safety story has an instructive arc: a surge of allergy reports in the 1990s crowned it allergen of the year in 2004, then careful chemistry showed the real culprits were impurities left by sloppy manufacturing. Purified CAPB is now considered among the safer surfactant choices, with a cautionary lesson baked into its history.

Where it comes from

Natural sources

  • Synthesized from coconut fatty acids and dimethylaminopropylamine (DMAPA)
  • The betaine head group makes it amphoteric — mild and pH-flexible

How it's made

Pale liquid; used at 2–15% in rinse-off products, 1–3% in leave-on.

What it does in products

  • Secondary surfactant and foam stabilizer
  • Mildness modifier for anionic surfactants (SLS/SLES)
  • Thickening in sulfate-free systems
  • Conditioning and anti-static effects

Benefits

Gentle cleansing

strong evidence

Reduces the irritation of primary surfactants, which is why it anchors baby and sensitive-skin cleansers.

Rich, stable foam

strong evidence

Stabilizes lather in hard water and sulfate-free formulas — a key reason formulators reach for it.

Low modern allergy rates

strong evidence

High-purity CAPB shows sensitization rates well under 1% in patch-test clinics — the 'allergen' reputation attaches to impure legacy material.

Side effects & safety

Allergic contact dermatitis (uncommon)Rates much lower with modern purified grades; patch-test confirmation advised.
Eye stinging in some formulas (uncommon)CAPB itself is mild; 'tear-free' claims depend on full formulation.

Safety considerations

  • Considered safe in rinse-off and leave-on products at regulated levels.
  • None.
  • Not for: Patch-test-confirmed CAPB allergy

How it's used

In supplements

Not a supplement ingredient.

In skincare

2–15% rinse-off; 1–3% leave-on.

Regulatory status

  • Permitted cosmetic ingredient; regulated through cosmetic safety standards.
  • INCI name on cosmetic labels: Cocamidopropyl Betaine.
  • CIR-reviewed and found safe, with impurity-limitation guidance (amidoamine ≤0.5%, DMAPA ≤100 ppm).

Popular products containing Cocamidopropyl Betaine

  • Cetaphil Gentle Skin Cleanser — CAPB-anchored mild cleansing systemCetaphil · Skincare
  • CeraVe Hydrating Cleanser — CAPB in the surfactant blendCeraVe · Skincare
  • Most tear-free baby shampoos — Industry-standard mild foam boosterVarious · Skincare

Product names and brands are shown for reference and belong to their respective owners.

The allergy arc

In the 1990s, CAPB allergy reports climbed steadily — but dermatologists noticed many patients reacted to the impurity fractions (amidoamine, DMAPA) rather than CAPB itself. The distinction matters because modern suppliers remove these byproducts; high-purity CAPB allergy rates in current patch-test data are typically under 1%, similar to or better than many alternatives. The episode shaped modern ingredient-purity standards.

How amphoteric surfactants work

CAPB carries both positive and negative charges depending on pH, which lets it insert between anionic surfactant molecules and reduce their denaturing effect on skin proteins. This 'spacing' effect is the chemistry of mildness — the same mechanism that makes betaines valuable in ophthalmics and baby products.

Frequently asked questions

Is cocamidopropyl betaine a sulfate?

No — it is a different chemistry and is often used to reduce sulfate irritation. 'Sulfate-free' products frequently rely on CAPB for foam.

Is CAPB safe for babies?

Yes — it is a standard component of tear-free and pediatric cleansers, with the mildness data to match.

Should I avoid CAPB if my skin reacts to shampoo?

If patch testing confirms CAPB allergy, avoid it. But many 'reactions' to shampoo trace to fragrance, preservatives, or sulfates — testing beats guessing.

The bottom line

Cocamidopropyl betaine is a genuinely gentle, well-characterized surfactant whose scary allergy history was mostly a manufacturing-purity problem — now largely solved.

References

  1. Cocamidopropyl betaine — Cosmetic Ingredient Review. CIR. https://www.cir-safety.org/ingredients
  2. CAPB allergy: impurity vs molecule. PubMed. https://pubmed.ncbi.nlm.nih.gov/19804438/
  3. Surfactant mildness in personal care. PubMed Central. https://pubmed.ncbi.nlm.nih.gov/31205280/