Chapter 2: Other surfactants · Part 4: Soap
Sodium and potassium cocoate
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The worst fact: in a 1997 study, most volunteers had to stop exposure to pure sodium laurate, coconut soap's main fatty acid salt, because of "burning sensations, erythema and/or scaling". The authors said this can't be applied directly to ordinary soap bars.
Why brands use it: coconut oil's main fatty acid is lauric acid. Potassium cocoate is made with potash.
Take care if: you have sensitive skin.
Comes from: coconut oil boiled with caustic soda (sodium cocoate) or potassium hydroxide (potassium cocoate).
Myth check: "Natural coconut soap is the gentlest": the shorter chains are the irritating ones. C10 chains are irritant, C12 (lauric) "minimally irritant", and C14 and longer not irritant.
Contaminants: nil. (Badly made soap can carry leftover caustic soda; see sodium tallowate.)
Fair to say: in irritation patch tests on 520 people, including people with eczema, a panel of mild surfactants that included 5% potassium cocoate gave few positive reactions, and a US cosmetic review found coconut oil soaps safe as used.
We use this ingredient. Potassium cocoate is the coconut half of the castile soap in our Bench Spray, Multi Purpose Cleaner, Clove & Eucalyptus Mould Spray, Glass Cleaner, Stainless Steel Cleaner, Pet Bedding Laundry Wash, Dog Wash and Castile Hand Wash. Our Laundry Liquid and Wool Mix use a soap made from coconut fatty acid and oleic acid, so it's in those too.
Correct as of November 2026. What the badges mean
Sources
- HERA. Alcohol ethoxylates (2009); esterquats (environment 2008, human health 2009); cocamidopropyl betaine (2005); fatty acid salts (2002).
- Tupker RA et al. Irritancy of sodium laurate. Skin Res Technol 1997, PMID 27333375.
The full source list is at the end of Chapter 2.