Supplementary Material for: Prevention of atopic dermatitis in babies by skincare from the newborn period

Background: So far, no definitive conclusions have been reached regarding the preventive effect of moisturizers on atopic dermatitis (AD). The variability in results may be due to differences in skin care methods, including bathing and washing, among studies and study design. In hot and humid Japan, bathing and gauze washing have been routinely practiced from the neonatal period, but this may impair the skin barrier function.
Objective: This study aimed to determine whether a combination of minimally invasive cleaning methods and moisturizing may prevent AD in infants in Japan.
Methods: Mothers of children born between January and September 2019 were instructed in traditional skin care methods (control group; 132 subjects), and mothers of children born between January and September 2020 were instructed in a new skincare method combining less invasive washing and moisturizing (intervention group; 140 subjects). Mothers and babies with and without a history of allergy were recruited, and the incidence of AD at one year of age was investigated.
Results: Skin care-related behaviors such as face washing, hand washing, and use of moisturizers were more frequent in the intervention group than in the control group. At 6 and 12 months of age, there was no difference in the incidence of AD between the two groups. However, for children born between January and March, the prevalence of AD at 12 months was significantly lower in the intervention group than in the control group (2.9% vs. 21.2%, P = 0.0253).
Conclusions: This study suggests that for children born during dry and cold seasons, strengthening the skin barrier function early in life through routine skin care with less invasive washing and moisturizing may prevent AD in Japan. Appropriate skin care practices for newborns and infants may vary in regions and environments.