n of the moisturizer container●●●Legend: *IgE* immunoglobulin E, *SCORAD* scoring atopic dermatitis, *TARC* thymus and activation-regulated chemokine, TEWL transdermal water loss

Sample size {#Sec18}
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In this study, the number of deliveries per month at the investigational site was estimated at 15--20, or more than approximately 200 childbirths per year. Moreover, with the current Japanese infant medical checkup system, it is unlikely that the mother will avoid the hospital in the first 4 months after delivery. Therefore, assuming a minimal recruitment rate of 70% and a less than 10% dropout rate, we expect a total of 120 (200 × 0.7 × 0.9 = 126) participants in our study. A questionnaire aimed at identifying the behavioral characteristics of mothers was created for the study to assess primary outcomes. Currently, there are no data showing the effectiveness of the survey sheet. Considering the inclusion of 60 subjects per group with a significance level of 0.05 and a standard deviation of 16 under the conditions described above, the expected upper limit of the standard error of the mean was approximately eight using a *t* test with a statistical power of 80%. Based on this estimate, the final target sample size was set at 120 patients. The statistical power was calculated using R ver.3.5.2 statistical software (R Foundation for Statistical Computing, Vienna, Austria).

Randomization procedure and concealment of allocation {#Sec19}
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Participants who meet the eligibility criteria and agree to participate in the study are randomized after signing the informed consent form. These subjects are stratified according to the estimated delivery date into winter and other seasons, and randomized using the permuted-block method. A statistical analyst generates a random allocation code using R statistical software (R Foundation for Statistical Computing) to randomize the subjects at each investigational site. The study is an assessor-blinded trial, 