Introduction: Moisturizers play an essential role in maintaining the integrity of the skin barrier by increasing stratum corneum hydration (SCH) and reducing transepidermal water loss (TEWL). According to dermatology and allergy guidelines, moisturizers should be applied on the skin within 3 min after bathing or showering. However, there is very little evidence supporting this recommendation. This study aimed to investigate the effectiveness of immediate and delayed moisturizing after bathing/washing on the improvement of SCH and TEWL.
Methods: This was a crossover study of 60 healthy Vietnamese volunteers aged 18-25 years. In each subject, SCH and TEWL levels were measured at three areas: non-moisturized, immediate moisturizing after washing, and delayed moisturizing at 30 min after washing.
Results: In non-moisturized skin, SCH and TEWL levels were significantly different from the baseline at 60 min after washing, while significantly decreased TEWL levels were observed immediately after moisturizing. In addition, moisturized skin had significantly higher SCH and lower TEWL levels compared with non-moisturized areas at every time point (p < 0.05). Interestingly, the percentage changes of SCH and TEWL levels from baseline did not differ between immediately and delayed moisturized areas.
Conclusions: Tested moisturizer helped increase SCH and decrease TEWL; however, there was no difference in moisturizing effectiveness between immediate and delayed moisturizing in healthy skin. The recommendation of immediate application of moisturizers after bathing/washing should be reconsidered, and more studies are needed to establish a stronger recommendation.
Keywords: SCH; TEWL; bathing; moisturizing; skin barrier.
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