Background: Poison ivy and poison oak are the most common causes of allergic contact dermatitis in North America. Objective: We investigated whether a new topical lotion containing 5% quaternium-18 bentonite prevents experimentally induced poison ivy and poison oak allergic contact dermatitis. Methods: A single-blind, paired comparison, randomized, multicenter investigation was used to evaluate the effectiveness and safety of quaternium-18 bentonite lotion in preventing experimentally induced poison ivy and poison oak allergic contact dermatitis in susceptible volunteers. One hour before both forearms were patch tested with urushiol, the allergenic resin from poison ivy and poison oak, 5% quaternium-18 bentonite lotion was applied on one forearm. The test patches were removed after 4 hours and the sites interpreted for reaction 2, 5, and 8 days later. The difference in reactions between treated and untreated patch test sites was statistically analyzed. Results: Two hundred eleven subjects with a history of allergic contact dermatitis to poison ivy and poison oak were studied. One hundred forty-four subjects had positive reactions to urushiol. The test sites pretreated with quaternium-18 bentonite lotion had absent or significantly reduced reactions to the urushiol compared with untreated control sites (p < 0.0001) on all test days. When it occurred, the reaction consistently appeared later on treated than on control sites (p < 0.0001). One occurrence of mild, transient erythema at the application site was the only side effect from the quaternium-18 bentonite lotion. Conclusion: Quaternium-18 bentonite lotion was effective in preventing or diminishing experimentally produced poison ivy and poison oak allergic contact dermatitis.
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