Cocamidopropyl betaine in shampoo and baby wash: what it is, and is it safe?

This is the fifth and last in our series on common ingredients worth knowing about, after triethanolamine, diethanolamine, methylisothiazolinone and phenoxyethanol. Cocamidopropyl betaine is the foaming ingredient in most "gentle", "sulphate-free" and "tear-free" washes, and it has an odd reputation: it was named Contact Allergen of the Year in 2004, and the biggest study ever done on it concluded it probably isn't an allergen at all. Both are true. Here's how.

What is cocamidopropyl betaine?

Cocamidopropyl betaine, usually shortened to CAPB, is a surfactant: a molecule with a water-loving end and an oil-loving end, which is what lets a wash lift grease off skin and hair and rinse away. It's made in 2 steps from coconut oil fatty acids, which is why labels sometimes call it "coconut-derived". It's an amphoteric surfactant, meaning it carries both a positive and a negative charge, which makes it much milder on skin and eyes than the sulphates (SLS, SLES) it's usually paired with or replacing. It also thickens and stabilises foam.

That mildness is why it's everywhere. When brands moved away from sulphates, CAPB was the obvious replacement, and in baby washes it has been the main cleanser for decades.

Where you'll find it

Shampoo and conditioner, body wash, liquid hand soap, facial cleansers and make-up removers, bubble bath, baby wash and "no tears" shampoo, shaving foam, toothpaste and mouthwash, intimate washes, contact lens solutions, wet wipes, and most "sulphate-free" products. In household goods: dishwashing liquid and some surface cleaners.

How to spot it on a label

• Cocamidopropyl betaine is the INCI name and what's usually printed
• Also written cocamidopropylbetaine, CAPB, coco betaine (a close relative, not identical), or cocoamphodiacetate and lauramidopropyl betaine for related amphoterics
• Raw-material trade names you won't see on a consumer label: Tegobetaine, Amphosol, Dehyton

It usually sits 2nd to 4th on a wash's ingredient list, after water and the main surfactant. In a "sulphate-free" product it's often 2nd, meaning it's the main cleanser.

Is cocamidopropyl betaine safe? What the research actually says

The 2004 "Allergen of the Year". Through the late 1990s and early 2000s, dermatology clinics in Europe and North America saw rising numbers of positive patch tests to CAPB: a 2008 review put the rate at 3% to 7% of patients tested. The pattern was eczema on the eyelids, face, scalp and neck from shampoo, and on the hands in hairdressers. The American Contact Dermatitis Society named it Contact Allergen of the Year for 2004. That is the origin of almost every "CAPB is toxic" article online.

The twist: it's probably the impurities, not CAPB. Making CAPB involves 2 chemicals that can be left over in the finished ingredient: amidoamine and dimethylaminopropylamine (DMAPA). Patch-test studies that tested these separately found that most people who reacted to "CAPB" reacted to DMAPA or amidoamine, and that purified CAPB with low impurity levels often didn't cause reactions at all. A Finnish occupational clinic found 15 allergic patients among 1,092 tested: 13 reacted to the amidoamine, 11 to DMAPA, and only 2 to CAPB itself.

The biggest dataset says "not a significant sensitiser". The German-speaking patch-test network reviewed 83,864 patients tested with CAPB between 1996 and 2009. About 2% tested positive, but almost all were weak reactions, the results could barely be reproduced when the same person was tested twice, and 4.6% of patients had irritant (non-allergic) reactions that are easy to misread as allergy. The authors' conclusion: the vast majority of positive CAPB results are false positives, true allergy is very rare, and CAPB is "not a significant skin sensitiser". A 2015 North American analysis of 10,877 patients found 1.4% positive to CAPB, with the impurities DMAPA and oleamidopropyl dimethylamine scoring higher.

What the regulators concluded. The US industry safety panel reviewed CAPB in 2012 and concluded it is safe when formulated to be non-sensitising, which in practice means keeping the DMAPA and amidoamine impurities low. The EU doesn't restrict it and doesn't classify it as a skin sensitiser. There is no evidence linking it to cancer, hormone effects or organ toxicity at cosmetic doses; it's a soap-like molecule that rinses off.

Irritation. Like every surfactant, CAPB strips some of the skin's own oils with repeated use. It does this far less than sulphates, which is why it's in baby products, but "mild" is not "nothing": if you wash your hands 30 times a day, the surfactant matters less than the frequency.

What the rules are

European Union. Permitted, no concentration limit, not classified as a sensitiser. The impurity question is left to manufacturers' quality control.

United States. No legal limit. The industry panel's "safe when formulated to be non-sensitising" standard is voluntary.

South Africa. No specific restriction. As with the other ingredients in this series, the EU position applies through the SANS cosmetics standard; the impurity level in any given bottle is unknown to you.

So should you avoid it?

For most people, no. Of the surfactants you could find in a wash, CAPB is one of the milder ones, and the allergy scare is largely a manufacturing-quality story that the better suppliers solved years ago. The practical exceptions:

1. Persistent eyelid, face or scalp eczema that tracks your shampoo or cleanser. Ask your dermatologist for a patch test that includes CAPB and amidoamine and DMAPA. Testing CAPB alone misses most true cases, and a weak positive to CAPB alone may be irritation, not allergy.
2. Hairdressers and anyone washing hands all day. Occupational hand eczema from CAPB-related compounds is documented. It's rare, but if your hands are cracked and you're in the trade, it belongs on the list.
3. Toothpaste and mouthwash reactions. CAPB is a recognised, if uncommon, cause of cheilitis (sore, peeling lips) and mouth irritation from toothpaste. If your lips flare and your toothpaste contains it, that's a cheap swap to test.
4. You already react to it. Then it's genuinely worth avoiding, and you'll have more work than most: it's in almost everything that foams.

If none of those apply, CAPB is not the ingredient to worry about in your bathroom. The isothiazolinone preservative and the fragrance in the same bottle are far more likely to cause a problem.

Frequently asked questions

Is cocamidopropyl betaine natural?
The fatty acids come from coconut oil; the rest of the molecule is synthetic. "Coconut-derived" is accurate and tells you nothing about safety either way.

Is it a sulphate?
No. It's often used instead of sulphates, or alongside them to make them milder. "Sulphate-free" products almost always contain it.

Is it safe for babies?
It has been the main cleanser in baby washes for decades precisely because it's mild on eyes and skin. True allergy is rare at any age. If a baby has eczema, the best wash is as little wash as possible, whatever the surfactant.

Is it the same as cocamide DEA?
No. Both are coconut-derived foam boosters and they're often confused. Cocamide DEA carries the nitrosamine and animal-cancer concern we covered in the DEA article; CAPB doesn't. Swapping DEA for CAPB is a step up.

What should a product use instead?
True soap needs no surfactant added. For non-soap washes, the other mild options are the glucosides (decyl glucoside, coco glucoside) and sodium cocoyl isethionate. All of them can irritate with overuse; none has a better allergy record than purified CAPB.

The sources

• Schnuch A, Lessmann H, Geier J, Uter W (2011). Is cocamidopropyl betaine a contact allergen? Analysis of network data and short review of the literature. Contact Dermatitis 64:203–211. 83,864 patients. View →
• Jacob SE, Amini S (2008). Cocamidopropyl betaine. Dermatitis 19:157–160. Review; the Allergen of the Year background and the 3–7.2% sensitisation estimate. View →
• Suuronen K, Pesonen M, Aalto-Korte K (2012). Occupational contact allergy to cocamidopropyl betaine and its impurities. Contact Dermatitis 66:286–292. View →
• Fowler JF et al. (2015). Cutaneous delayed-type hypersensitivity to surfactants. Dermatitis 26:268–270. North American Contact Dermatitis Group, 10,877 patients. View →
• Burnett CL et al. (2012). Final report of the Cosmetic Ingredient Review Expert Panel on the safety assessment of cocamidopropyl betaine. International Journal of Toxicology 31(4 Suppl):77S–111S. Industry panel. View →

Find out more

• Diethanolamine (DEA) and cocamide DEA: dangers and is it safe?
• Methylisothiazolinone (MI): the allergy epidemic explained
• Phenoxyethanol: the paraben replacement, and is it safe?
• Triethanolamine: dangers, side effects and is it safe?
• Commercial soap ingredients: what's really in your bottle

This article is general information, not medical advice. If you have a skin reaction that doesn't settle, see a doctor or dermatologist and ask about patch testing.

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