By toxicologist Ewa Daniél
What is it?
Cocamidopropyl Betaine also called CAPB is a fatty acid amide derived from coconuts. It has several functions in cosmetic products, but it is mainly used as a surfactant or because of it’s cleaning properties in cosmetic rinse off products such as shampoos, liquid soaps and other bathing products.
These product’s abilities to clean and rinse often have an unwanted side effect; namely to cause skin irritation since they remove fats from the skin. The reason why CAPB is popular, is because it is less irritating compared to other surfactants and detergents such as for example Sodium Lauryl Sulfate which is frequently used in cosmetic products, especially shampoos and bathproducts.
So what is the problem?
As seen with other ingredients that have been widely used for a long time, there have been cases of allergy to CAPB. In 2004 the American Contact Dermatitis Society voted it to be “Allergen of the year.” This was however a bit premature, since many tests and studies have shown that its not the pure Cocamidopropyl Betaine that causes the allergy, it actually has a very low sensitizing potential. The allergic reactions are in fact caused by impurities in CAPB.
In the US several studies have showed that it is Aminoamide (AA) in CAPB that causes the allergy, whereas numerous European studies demonstrates that it is 3-dimethylaminopropylamine (DMAPA) that causes the allergy. The difference here is probably due to the fact that American consumers are more often exposed to AA and vice versa in Europe.
What do the experts say
A large study was conducted with an analysis of network data and reviews of literature to find out if Cocamidopropyl Betaine actually is a contact allergen. The analysis showed that the evidence of CAPB being allergenic is very limited, positive reactions to patch test preparations containing CAPB were suspected to be caused by the impurities DMAPA and AA:
It has repeatedly been shown that CAPB patch test positives do not (or very rarely) react to highly purified CAPB.
In predictive animal testing, it was classified as a non-sensitizer.
Pure CAPB was not shown to be a skin sensitizer, in either humans or animal tests.
Both commercially marketed CAPB and CAPB patch test preparation incorporating CAPB from different sources probably contain impurities to different degrees. Among these, DMAPA is present at a concentration that is most likely far too low, whereas AA may be present at a high enough concentration to cause sensitization and elicitation, at least in a small subgroup of susceptible individuals.
1991 – The Final Report on the Safety Assessment for Cocamidopropyl Betaine (CAPB) was published in the Journal of the American College of Toxicology with the conclusion: CAPB is safe for use in rinse off products at the current levels of use. The concentration of use for products designed to remain on the skin for prolonged periods of time (leave on)should not exceed 3.0%.
April 2007 -The CIR Expert Panel reopened the final report on CAPB based on new published data that described sensitization in patients from use of rinse off products, new uses in aerosol products, and a substantial increase in the number of uses. Sensitization may be due to impurities found in CAPB.
July 2008 – CIR issued a Scientific Literature Review.
September 2008 – The CIR Expert Panel discussed at length the issue of the impurities DMAPA and AA in CAPB. The Panel considered placing concentration limits on these two sensitizing impurities, but the available data gave conflicting accounts as to thresholds of sensitization, especially for the AA. The Panel concluded that CAPB is safe for use in cosmetic formulations in the present practices of use and concentration, provided that the content of DMAPA and AA are not high enough to induce sensitization. The CIR Expert Panel advised that human repeat insult patch tests be undertaken by industry to demonstrate conformance with this conclusion. A Tentative Amended Report was issued.
December 2008 – The CIR Expert Panel decided to table the Draft Final Amended Report on CAPB in order to gather more safety information on the impurities DMAPA and AA. The Panel decided to consider potentially expanding the report with the addition of related amidopropyl betaines.
Human and Environmental Risk Assessment/Hera project: Based upon the low frequency of positive diagnostic patch test reactions to CAPB and the outcome of predictive animal tests, the sensitizing potential of CAPB is considered low, especially given its widespread distribution in cosmetic and detergent products. Furthermore, the extensive body of data documenting the ability of impurities in CAPB to cause skin sensitisation demonstrates that the risk of contact allergy can be minimised by strictly controlling the levels of AA and DMAPA in CAPB. This can be achieved practically by using a higher grade of the material.
August 31, 2010 – The CIR Expert Panel issued a tentative report with the conclusion that CAPB are safe for use in cosmetic products when formulated to be non-sensitizing based on the quantitative risk assessment for sensitization.
Studies show that the purified CAPB is not allergenic, but allergy is caused by the impurities DMAPA and AA. AllergyCertified can allow purified CAPB in rinse off products. AllergyCertified always get documentation for this before a product can be certified. This means that when you see a product we have certified containing CAPB, you can rest assured that we have examined the impurities in Cocamidopropyl Betaine and know the exact levels of AA and DMAPA.
Angelini G. et al “3-Dimethylaminopropylamine: a key substance in contact allergy to Cocamidopropylbetaine?” Contact dermatitis: Vol. 32, Issue 2, February 96–99;1995
Angelini G. et al; “Contact allergy to impurities in surfactants: amount, chemical structure and carrier effect in reactions to 3-dimethylaminopropylamine” Contact dermatitis: vol. 34 issue 4 April, 248-252; 1996
CIR, “Final amended report on Cocamidopropyl betaine and related Amidopropyl betaines 2010
CIR” Final report on the safety Assessment of Cocamidopropyl Betaine; jour. Am. Col. Tox vol 10 no. 1, 1991
Schnuch A et al; “Is Cocamidopropyl betaine a contact allergen? Analysis of network data and short review of the literature” Contact Dermatitis, vol. 64, 203–211; 2011
HERA -Human and Environmental Risk Assessment on ingredients of household cleaning products. Cocamidopropyl betaine (CAPB) Edition 1,0 June 2005
Burnett C.L et al” Final rreport of the cosmetic Ingredients Review expert panel on the safety Assessment of Cocamidopropyl betaine (CAPB) Int. journ. Toxicol 775-1115; 2012