RESUMO
It has been discovered that all individuals who are allergic to cocamidopropyl betaine (CAPB) are sensitized to 3-dimethylaminopropylamine (DMAPA) and to amidoamine, molecules which are intermediaries in CAPB synthesis, and which persist as impurities in the material that is sold; the amounts vary, depending on the quality of the CAPB in the end product. We present three cases of allergic contact dermatitis to DMAPA. In all three cases, the skin tests for DMAPA were positive, while there was no reaction to CAPB. The current relevance of these tests was confirmed by the patients' re-exposure to the suspect products themselves, which contained CAPB. Contact allergy to CAPB is now infrequent, partly because of the increasing use of new non-irritating surfactants that have been introduced on the market in the last decade. However, cases of patients allergic to commercial CAPB who only react to DMAPA -and not to CAPB- when they are patch tested are still being reported. DMAPA itself, and other molecules like amidoamine, would be the true allergens, and some cases of CAPB allergy are therefore being overlooked because DMAPA is not always included in the cosmetics series. CAPB may no longer be necessary in patch tests, as DMAPA seems to be the principal allergenic fraction in this surfactant, and also because manufacturers of skin allergens currently prepare CAPB extracts that are so pure that they are no longer a good screening tool for contact allergy to commercial CAPB.
