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BACKGROUND: Moisture barriers are an important element in a well structured patient skin care program. Dimethicone (1% to 30%) is one of several ingredients approved by the FDA as active ingredients for OTC skin protectant drug products. Manufacturers generally rely on the FDA Skin Protectant Drug Monograph as documentation of efficacy. However, this monograph only specifies allowable active ingredients and ranges of ingredients, but does not specify tests to assure product efficacy. Excipients which deliver the active ingredient to the skin can greatly affect performance of the product; however, they differ considerably between products. Therefore, it is imperative that manufacturers provide documentation of claims beyond simple reliance on published monographs.
METHODS: It is well documented that as the skin becomes increasingly hydrated, there is a corresponding increase in electrical conductivity. Efficacy of four dimethicone moisture barriers was assessed by their effectiveness at preventing this increase in conductance following exposure to a standardized water challenge. All four products were tested in a randomized fashion on the forearms of 36 healthy volunteers using a previously published procedure which sequentially follows products through multiple standardized water challenges and simulated normal washes. This procedure tests the products both for initial moisture barrier effectiveness and for wash-off resistance.
RESULTS: There were significant differences in the moisture barrier effectiveness between the four products throughout the study (p<0.0001, ANOVA with Tukey’s pairwise comparisons). These differences were apparent initially after application and through three simulated normal washes.
CONCLUSIONS: These results emphasize the need for manufacturers to substantiate moisture barrier claims even if it is not a requirement of the OTC drug monograph.