In many natural cosmetics products, cocamidopropyl betaine (CAPB) is used as an alternative to less fine foaming agents such as the sulphates SLS or the somewhat milder variant SLES. Which not only strip dirt, but also natural fats from your scalp. And thus affect your skin barrier.
This ensures that your skin is no longer well protected. Which can cause irritation, skin flaking and allergy. If you have colored hair, your hair color can fade faster when using products with SLS.
Your skin will also produce extra sebum to compensate for the loss of skin fat. Which can lead to hair loss. That doesn't sound all that festive. You can imagine that a natural alternative like CAPB was received with cheer by cosmetics country.
Is Cocamidopropyl a Safe Foaming Agent?
We regularly receive questions from people about a shampoo without CAPB, based on an allergy test they have done. Where CAPB comes out as one of the skin irritating/allergy-causing ingredients. But is this representative of the entire population?
Is CAPB safe or not as an ingredient in a cosmetic product? That's what I wondered. From our experience, and past studies where it is labeled as a skin irritant. Because CAPB is (still) used by quite a lot of natural brands - including new brands. And because it is a COSMOS approved ingredient. What is the latest state of scientific research on CAPB?
Based on the latest insights, is it a safe foaming agent for your shampoo or other foaming product? Or is it better to (continue to) avoid it?
What is Cocamidopropyl Betaine?
Cocamidopropyl betaine is a foaming agent derived from coconut oil. It cleans and gives a nice foam. That is why it is loved as a skin and environmentally friendly alternative to SLS or SLES.
What does research say?
Cocamidopropyl Betaine is a mild foaming agent. However, studies have shown it to be a skin irritant. The irritation is caused by CAPB itself or pollution that can be produced during its production.
It appears to be more of a skin irritant than a contact allergen. However, studies are not entirely clear on this. My conclusions from the studies I have gone through: rather not products with CAPB. Or don't use more than a few products that contain it. And that are produced very pure. The latter, however, is difficult to verify.
Conclusions from scientific studies
- Data from the Information Network of Dermatology Department from 1996 to 2009, testing nearly 84,000 people with a solution of 1% CAPB in water, showed that the chance of an allergic reaction was relatively small. The risk of an allergic reaction was higher for men aged 40 and over with atopic or scalp eczema. With the profession of hairdresser (where you often work with foaming shampoos). Or from a 48-hour patch test (your skin is exposed to CAPB for 48 hours - many foaming products, however, are rinse-off products). 
- In 2004, CAPB was named allergen of the year, because more and more people were experiencing an allergic reaction after using products with CAPB. Because it can only give a relatively mild skin irritation reaction, CAPB was increasingly used in various cosmetic products. Which increased the chance that the skin comes into contact with it more often. And the chance of a skin reaction increases. Impure substances released during the production process probably play an important role in triggering a negative skin reaction. [ 2 ] [ 3 ]
- It is suspected that allergic reactions to CAPB are caused by impurities in CAPB; dimethylaminopropylamine and cocamidopropyl dimethylamine. Patch test data between 2002 and 2009 show that no less than 39% of the 1092 people tested had a skin irritating reaction to at least one of the substances. Allergic reactions were much less, in only 1.3% of those tested. [ 4 ]
- Research in 2021 shows that CAPB is one of the ingredients that many people have an allergic reaction to. Partly because the ingredient is used in so many products. [ 5 ]
- In combination with the use of CAPB with other specific cleaning agents, the chance of a skin reaction is relatively high [ 6 ]
- A review of cosmetics that cause contact allergy in 2022 shows that CAPB is more of an irritant than an allergy-triggering ingredient [ 7 ]
- Research in Beijng hospital among 429 people shows that 5% have an allergic reaction to CAPB (2008) [ 8 ]. A study in the USA in 2004 among 975 people showed an allergy rate of 1.5% (15 people) for CAPB. Which is a relatively small percentage. [ 9 ]
Other SLS/SLES alternatives than CAPB
Examples of other alternative foaming agents used for SLS or SLES are:
- Decyl glucoside : gives a mild foam. Is vegetable (SLES/SLS come from the petroleum industry) and biodegradable. Is gentle on your scalp. Generally not irritating. Doesn't dry out your skin. However, a number of studies indicate that decyl glucoside may cause allergy. Is COSMOS approved.
- Sodium Cocoyl Sarcosinate : mild and non-irritating to the skin. Vegetable. Derived from coconut. Can ensure that other ingredients in a product are absorbed more quickly by your skin. If these are pure ingredients, this is fine. 
- Disodium Cocoyl Glutamate: Also a derivative of coconut. Mild and gentle on the skin. A number of studies have shown that it can irritate the skin. But this is at a high(er) dose than occurs in shampoos, for example. The question is what the stacking effect is when using multiple products with the ingredient. Could be harmful to the environment. Approved by natural quality marks NaTrue and Ecocert.
- Soap nut/berry (Sapindus) : contains saponins that provide a mild lather. Has been used since 5000 years ago for its therapeutic qualities  . Among other things as a remedy for eczema and psoriasis. Is an important Ayurvedic ingredient in shampoos and cleansers.
- Sodium Coco Sulfate : is still a sulfate. Milder than SLS or SLES, but still a skin irritant that can affect your skin barrier. And probably harmful to the environment.
- Sodium Cocoyl Isethionate: Foaming cleanser. Does not penetrate the skin. As a result, the skin barrier is not or less damaged.  Is a relatively expensive ingredient, so it is less often used in cosmetics.
- Sodium Lauryl Sulfo-Acetate: Foaming cleanser. No sulfate. Milder than SLS/SLES. But depending on the concentration an irritant to skin, eyes and respiratory tract.