Clinical allergy to cocamidopropyl betaine: reactivity to cocamidopropylamine and lack of reactivity to 3-dimethylaminopropylamine.

7 patients allergic to cocamidopropyl betaine (CAPB) were detected by positive patch test reactions to Tegobetaine L7TM. These patients were then asked to participate in further testing to its potential impurities, cocamidopropylamine and 3-dimethylaminopropylamine (DMAPA). 4 of the 7 patients were tested to purified CAPB and cocamidopropylamine, with 2 reacting to the purified betaine on allergy patch testing and 3 reacting to cocamidopropylamine 0.1%. At another date, 6 of the 7 were successfully recalled for testing to DMAPA in the presence of sodium lauryl sulfate (SLS) or pure CAPB; 1/6 reacted to DMAPA in water, but only at very high concentrations, at least 3 orders of magnitude higher than that to which skin exposure would occur from use of products containing CAPB. Both SLS and CAPB increased the number of reactions recorded to high levels of DMAPA. However, positive reactions to much lower concentrations of DMAPA (>or=100 ppm) were found in only 1/6 subjects and then only in the presence of the irritant SLS. 0/6 reacted to pure CAPB alone. Taken together, these results suggest that DMAPA is unlikely to be an important contact allergen in CAPB of appropriate quality. They also confirm that CAPB of suitable purity, where levels of both cocamidopropylamine and DMAPA are minimized, is unlikely to trigger reactions in those ostensibly allergic to the material.