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Chapter 2: Other surfactants · Part 3: Amphoteric surfactants

Cocamidopropyl hydroxysultaine (CAHS)

  • Contaminant risk
Also called
CAHS, sultaine, cocamidopropyl hydroxy sultaine
Found in
skin cleansers, bath products, cleaners

The worst fact: it was a severe eye irritant in rabbits at up to 41.5%.

Why brands use it: a co-surfactant. It's used at up to 11.5% in skin cleansers and 6.8% in bath soaps and detergents; a related sultaine assessed in Australia was notified for use in acid, bleach, bathroom and glass cleaners at up to 10%.

Take care if: you're allergic to CAPB or its impurities: a 2026 case series (a letter) reported patients who reacted both to a CAHS facial cleanser and to dimethylamines and amidoamine, impurities also linked to CAPB allergy.

Comes from: the same coconut amidoamine as CAPB, reacted with sodium 3-chloro-2-hydroxypropanesulfonate, which is itself made from epichlorohydrin (Australia: "May cause genetic defects; May cause cancer"). That's one step further back than this book's 🛢 badge counts, the same as the acrylonitrile behind CAPB's DMAPA.

Myth check: no common myth we could source.

Contaminants: DMAPA (Australia: "May cause an allergic skin reaction."), reported at under 2 to under 10 ppm. They're unlikely in a well-made product, but it's a factor you can't see on the label.

Fair to say: it didn't cause allergy in human patch tests at up to 4%, and a US cosmetic review (2024) found it safe as used.

Correct as of November 2026. What the badges mean

Sources

  • Safe Work Australia. Hazardous Chemical Information System (HCIS): classifications for alcohol ethoxylates, C10-12 alcohol EO/PO, cocamidopropyl betaine, nonylphenol, DODMAC, and for ethylene oxide, propylene oxide, dimethyl sulfate, methyl chloride, benzyl chloride, epichlorohydrin, DMAPA, monochloroacetic acid and 1,4-dioxane.
  • HSDB (US National Library of Medicine), via PubChem, including Gosselin, Clinical Toxicology of Commercial Products (1984); ECHA C&L Inventory (company notifications, via PubChem); JECFA, sodium oleate (via PubChem).
  • Cosmetic Ingredient Review: alkyl glucosides (2013); poloxamers (2008); cocamidopropyl betaine and amidopropyl betaines (2012); alkyl betaines (2018); alkyl sultaines (2024); lauriminodipropionates (2013); coconut oil and related ingredients (2011); fatty acids and fatty acid salts (2019).
  • Weber B et al. Co-reactivity of a cocamidopropyl hydroxysultaine-containing facial cleanser with dimethylamines and amidoamine (letter, 2026), PMID 40936378.

The full source list is at the end of Chapter 2.