CONTACT ALLERGY TO IMPURITIES IN SURFACTANTS - AMOUNT, CHEMICAL-STRUCTURE AND CARRIER EFFECT IN REACTIONS TO 3-DIMETHYLAMINOPROPYLAMINE

Since finding that all subjects with contact allergy to cocamidopropyl betaine give positive reactions to 3-dimethylaminopropylamine (DMPA), we wished to verify whether sensitization to other industrially-used t ensioactives might also be due to content of DMPA as an impurity. We a lso investigated the possible ''carrier action'' that tensioactives mi ght exert on minimal quantities of DMPA. Finally, we analyzed the rela tionship between the structure of DMPA and other chemically-correlated molecules and their sensitizing potential, with particular reference to the structure of alkylamidopropylbetaines. For this purpose, in 34 patients with contact allergy to DMPA, we tested: (i) DMPA in concentr ations below the threshold limit in water and in different tensioactiv es; (ii) substances that employ DMPA as a reagent in their synthesis; (iii) substances similar to DMPA as regards chemically reactive groups . The study showed that: (i) DMPA remains as a quantitatively detectab le impurity in all tensioactives employing it in their synthesis; (ii) some common anionic (SLES) and non-ionic (polysorbate 20) tensioactiv es enhance the risk of sensitization from very low doses of DMPA, pres umably due to a ''carrier effect;'' (iii) the sensitizing chemical str uctures in DMPA and related molecules are the primary amine and the te rtiary (dimethyl-substituted) amine groups, when separated by either 2 or 3 carbon atoms; (iv) no sensitizing action can be attributed to th e functional groups present in alkylamidopropylbetaine molecules.