Background: There is no general agreement on whether cocamidopropyl betaine (CAPB) is a skin sensitizer.
Objective: To examine the evidence for CAPB being a (non-)sensitizer.
Methods: This was a retrospective analysis of data on patch testing with CAPB 1% aqua collected by the Information Network of Departments of Dermatology from 1996 to 2009, with a focus on the patch test reaction profile, and demographic and clinical features of CAPB positives, supplemented by a literature review.
Results: Eighty-three thousand eight hundred and sixty-four patients were patch tested with CAPB 1% aqua, yielding 2.16% [95% confidence interval (CI) 2.06-2.26%] positive (2.03% + and 0.13% + + /+ + + ) and 4.6% non-allergic reactions. Thus, the reaction index was-0.368 and the positivity ratio was 94.2%. Reproducibility on synchronous patch testing (n = 6534) was poor [Cohen's kappa: 0.29 (95% CI 0.25-0.32)] and results upon retesting (n = 1157) were almost non-reproducible [kappa: 0.12 (95% CI 0.05-0.19]. Multifactorial logistic regression analysis revealed an increased risk associated with being male and aged ≥40 years, with atopic dermatitis, with scalp dermatitis, with being a hairdresser, and with a 48-hr patch test application. When only + + or + + + reactions were used as a conservative outcome, only the elevated risk in males and in patients with atopic dermatitis remained significant.
Conclusion: The vast majority of positive reactions to CAPB are presumably false positive. Allergic reactions are very rare. This would support the notion of CAPB being 'not a significant skin sensitizer', in line with current classification systems.
© 2011 John Wiley & Sons A/S.