Do you prefer a foaming shampoo to a non-foaming one? Me, too! The ingredient that creates lather is called a surfactant, or cleansing agent. In this post, you will learn about cocamidopropyl hydroxysultaine – one of many newly emerging surfactants that is especially popular in shampoos for curly hair. In addition, you will see it in shampoos marketed as natural, plant-based, and non-toxic. This surfactant shares the first word in its name with another cleansing agent, cocamidopropyl betaine (CAPB), and is often used in its place. We will also look at the seemingly related substances of cocamidopropyl hydroxysultaine, cocamidopropyl betaine and coco betaine.
So, just how safe and effective is this surfactant? Read on!
The skinny on cocamidopropyl hydroxysultaine
To begin with, when I research a product or an ingredient, I look at a variety of sources. They include Cosmetic Ingredient Review (CIR) Expert Panel reports as well as information from the European Chemicals Agency database and the American Contact Dermatitis Society. In addition, I browse through the latest scientific and medical studies in the National Library of Medicine and printed medical journals. And, of course, I check what is probably the first source that comes to your mind – the Skin Deep database powdered by the Environmental Working Group (EWG).
EWG Skin Deep database
While this database is one of the most helpful tools to assess the safety of a product or an ingredient, it has some shortcomings. For example, some ingredients with a rating of 1 out of 10 (with 1 as the safest) have limited or no safety data. This is true for both cocamidopropyl hydroxysultaine and coco betaine. Unlike cocamidopropyl betaine, which has a rating of 1-6 with a good amount of safety data available, cocamidopropyl hydroxysultaine and coco betaine each has a rating of 1 with limited safety data (source and source).
Additionally, sometimes the EWG database does not reflect the latest research on product ingredients. For instance, it often cites the CIR reports, but it does not seem to reflect their findings.
Therefore, instead of relying on the Skin Deep database’ ratings, I go directly to the sources it cites and form my own opinion. By doing this type of research, I set my standards for products that I use and promote on my blog. I also do this research for companies that are in the process of selecting ingredients for their new products.
If you want to learn how to use the Skin Deep database the right way, please read my post about it.
Cosmetic Ingredient Review reports
As for the CIR reports, they come from the Cosmetic Ingredient Review (CIR) Expert Panel. The CIR Expert Panel is an industry-sponsored agency, which means it is not independent of the industry. This is something to keep in mind while reading the reports, even though they are helpful and a good source of scientific studies.
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Is cocamidopropyl hydroxysultaine safe?
To answer this question, let us look at the main points from the CIR report of 2018 and the process of its production.
The CIR report points
- First, the scientists did not find this surfactant genotoxic in concentrations up to 50%.
- Second, just as cocamidopropyl betaine, they described it as a severe eye irritant.
- Third, in animal studies in concentrations up to 41.5%, the researchers did not find this ingredient irritating to skin.
- However, in 45% of 44 healthy people in a concentration of 2.5%, the researchers observed slight to moderate irritation after repeated patches.
- Further, in a patch test using a concentration of 4% on 51 healthy volunteers, the scientists observed no irritation or sensitization.
- Also, the surfactant (1%) yielded positive patch tests in a patient that experienced eczema following the use of 2 shampoos that contained this ingredient.
- Lastly, there are no published studies as to whether it might be carcinogenic.
In conclusion, the Panel stated that the sensitization potential of this ingredient is very low. If sensitization occurs, it is most likely due to the presence of 3,3-dimethylaminopropylamine (DMAPA) as a contaminant (see below). To clarify, sensitization is an allergic reaction that affects the immune system after previous exposure. In other words, you can be fine after the first use of the product but may develop an allergic reaction later (source).
Cocamidopropyl hydroxysultaine manufacturing process
Sometimes, knowing how an ingredient is made is as important as knowing what it is made of. Thus, the production of this surfactant is a multi-step process where chemicals are added to produce intermediary chemicals. As a result, this cleansing agent may have some contaminants in it. Specifically, 3,3-dimethylaminopropylamine (DMAPA) is a cause for concern even in tiny amounts because it is a sensitizer. As a matter of fact, cocamidopropyl betaine has this contaminant, too.
According to one supplier, generally this ingredient contains less than 2 ppm (parts per million) of DMAPA. Another supplier reported that unreacted free DMAPA is typically less than 10 ppm.
To ensure that fewer people have sensitization to this ingredient, the CIR Expert Panel urged manufacturers to minimize the content of DMAPA.
In addition to the studies described in the 2018 CIR report, I found one related case of an allergic reaction to this surfactant.
Is cocamidopropyl betaine safe?
To begin with, CAPB is structurally related to and has been studied a lot better than cocamidopropyl hydroxysultaine. Specifically, the CIR Panel issued two reports on this ingredient in 1991 and in 2012. In the latest report, the Panel recognizes that CAPB has the potential to induce skin sensitization. Most likely, the sensitization occurs due to the contaminants DMAPA and amidopropyl dimethylamine (amidoamine). Hence, the Panel advises that manufacturers continue minimizing the concentration of sensitizing impurities.
In addition, Dutch dermatologists recommend that hairdressers should patch test for allergy to CAPB when they use products containing this ingredient.
Furthermore, the American Society of Contact Dermatitis lists it as one of the core allergens, even in concentrations as low as 1%. Due to high rates of cases involving allergic reactions, the society named it Allergen of the Year in 2004.
On the other hand, Spanish dermatologists believe that an allergic reaction to CAPB is infrequent. They reported cases of patients with an allergy to DMAPA but not to CAPB. Also, German dermatologists argue that the vast majority of positive reactions to CAPB are presumably false positive.
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What is coco betaine?
First of all, is coco betaine the same as cocamidopropyl betaine? The answer is no. Thus, they have different Chemical Abstracts Service (CAS) Registry numbers: 68424-94-2 and 86438-79-1 respectively.
Per the 2018 CIR safety assessment report, this cosmetic ingredient belongs to the group of alkyl betaines along with lauryl betaine, cetyl betaine, and myristyl betaine. Just like cocamidopropyl hydroxysultaine, it functions as a hair and skin conditioning antistatic surfactant, and as a viscosity increasing agent.
Coco betaine manufacturing process
According to the report, the manufacturers make this surfactant by reacting coconut fatty acids with chloroacetic acid, not DMAPA. This is a big distinction. To clarify, there is no risk of DMAPA contamination. Consequently, there is no risk of sensitization or allergic reaction from DMAPA.
It appears that manufacturing of other surfactants whose names end in -dopropyl involves DMAPA. They include cocamidopropyl hydroxysultaine, erucamidopropyl hydroxysultaine, lauramidopropyl hydroxysultaine, myristamidopropyl hydroxysultaine, oleamidopropyl hydroxysultaine, tallowamidopropyl hydroxysultaine, lauramidopropyl betaine, and avocadamidopropyl betaine, to name a few.
Nevertheless, coco betaine is not completely harmless.
Is coco betaine safe?
Unlike cocamidopropyl betaine, coco betaine was not sensitizing in either animal or human dermal studies in concentrations up to 5%. Additionally, in animal tests for irritation in concentration at 16%, researchers found it not irritating.
On the other hand, it was tested together with sodium laurel sulfate (SLS) in distilled water for dermal irritation on 27 humans with 24-hour exposure. As a result, the mean overall scores for coco betaine and SLS were 1.03 and 1.833, respectively. That is to say, though less than SLS, it had some irritation potential.
Further, there are reports of two cases of eczematous lesions following exposure to shampoos containing this ingredient (1).
In sum, after considering the available data on alkyl betaines, the Panel noted low systemic toxicity in animal studies, no reproductive/developmental toxic effects in animal studies, no genotoxicity in in vitro studies, and no sensitization in multiple tests. The CIR Panel concluded that coco betaine was safe in cosmetics when formulated to be non-irritating.
Conclusion about cocamidopropyl hydroxysultaine
In conclusion, I believe that the concerns of sensitization to cocamidopropyl betaine have relevance to cocamidopropyl hydroxysultaine. Therefore, the lack of safety data does not make it a safer alternative to cocamidopropyl betaine. In my Shampoo Rating List, I give it a rating of 3 out of 10 (with 10 as the worst) versus the rating of 1 in the Skin Deep database. I would definitely avoid using products with these two ingredients on babies and suggest using an all-natural shampoo bar instead. I have been using a soap bar on my son since he was born and his hair is shiny and silky.
Nonetheless, despite its potential for sensitization, it is not one of the worst surfactants, in my opinion. Even the safest and gentle glucoside surfactants are not as innocuous as previously thought.
In addition, there is some evidence that manufacturers started sourcing the purest version of these two ingredients without the sensitizing contaminants. Hence, if you buy products with these ingredients, make sure you are buying from reputable companies. Also, proceed with caution and discontinue using the product if irritation occurs.
Lastly, book a consultation with me for personal help with non-toxic living and browse my shop for safe products. Best of all, join the Savvy Consumer Circle to become a part of a healthy-living community.
(1) Van Haute N, Dooms-Goossens A. Shampoo dermatitis due to coco betaine and sodium lauryl ether sulphate. Contact Dermatitis. 1983; 9(2): 169-169.
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