Optimal application method of a moisturizer on the basis of skin physiological functions

BACKGROUND: Clinical studies have clarified the usefulness of moisturizers for dry skin diseases. However, few reports exist on the appropriate application of moisturizers with respect to the skin physiological functions. AIMS: To clarify the optimal moisturizer application method on the basis of skin physiological functions. METHODS: This study investigated the appropriate time, dose, and frequency of moisturizer application from the perspective of skin physiology. In healthy subjects, the stratum corneum water content (SCW) was compared between different moisturizer application times (immediately [≤5 min] and 90 min after bathing), doses (0.5, 1.0, and 2.0 mg/cm(2)), and frequencies (once and twice daily). Thereafter, patients with dry skin were treated with the moisturizer once or twice daily for 8 weeks at the time, and application dose was determined to be optimal for the healthy subjects; the moisturizing effect was evaluated based on the SCW, trypsin activity, and desmoglein 1 localization score in the stratum corneum. RESULTS: In healthy subjects, compared to at control sites, the SCW was significantly higher at sites treated with the moisturizer immediately after bathing, with 1.0 and 2.0 mg/cm(2) of the moisturizer, and with once‐ and twice‐daily applications. In patients with dry skin, the SCW was significantly higher compared to control sites and the desmoglein 1 localization score was significantly lower after 8 weeks only when the moisturizer was applied twice daily. CONCLUSIONS: Moisturizer application of ≥1.0 mg/cm(2) twice daily (immediately after bathing at night and in the morning) had a moisturizing effect, as verified from the skin physiological functions.