Epidemiology and Co-Reactivity of Novel Surfactant Allergens: A Double-Blind Randomized Controlled Study

Background Surfactants are cleansing agents used in products such as shampoos and soaps. Objectives The aims of this study were to identify positivity rates to 3 novel amide-containing surfactants (sodium lauroyl sarcosinate, isostearamidopropyl morpholine lactate, and disodium lauroamphodiacetate) and evaluate co-reactivity with other surfactants in patients with known surfactant sensitivity. Methods Previously patch-tested, surfactant-positive patients were identified via chart review and invited to participate. Participants were patch tested to screening surfactants (cocamidopropyl betaine, amidoamine, dimethylaminopropylamine, cocamide diethanolamine [DEA], oleamidopropyl dimethylamine, and decyl glucoside), as well as 3 novel surfactants: sodium lauroyl sarcosinate 0.5% and 1.0% aq, isostearamidopropyl morpholine lactate 0.5% and 1.0% aq, disodium lauroamphodiacetate 1.0 and 2.0% aq, and a hypoallergenic liquid cleanser (tested semiopen). Participants and clinicians were blinded. The order of tested allergens was randomized. Results Forty-seven participants completed the study. Excluding doubtful reactions, positive reactions were most common to oleamidopropyl dimethylamine (34%) and dimethylaminopropylamine (34%), followed by isostearamidopropyl morpholine lactate (23%). Reactivity was not associated with history of childhood eczema. Co-reactivity was high among oleamidopropyl dimethylamine, dimethylaminopropylamine, cocamidopropyl betaine, amidoamine, and isostearamidopropyl morpholine lactate. None of the participants who reacted to cocamide DEA reacted to an additional surfactant. Conclusions Isostearamidopropyl morpholine lactate may be an important emerging allergen with sensitivity rates comparable with those of oleamidopropyl dimethylamine and dimethylaminopropylamine. Co-reactivity among surfactants was frequent except for cocamide DEA.