Supplementary Material for: Comparison of Skin Structural and Functional Parameters in Well-Nourished and Moderately Undernourished Infants

<b><i>Background:</i></b> Little is known about the impact of nutrition on the development of skin structure and function in infants. <b><i>Methods:</i></b> We investigated epidermal, dermal, and subcutis parameters of aged-matched well-nourished and moderately undernourished infants in this single-center, cross-sectional, noninterventional study using noninvasive methods (skin caliper, 20-MHz sonography, transepidermal water loss, skin pH, and corneometry). Plasma fatty acids were determined as an indicator of nutritional differences. 310 infants from different age groups, i.e., 1 week, 4 weeks, and 6, 9, 12, 24, and 36 months were included. Approximately half of each age group was well-nourished (WHO reference values weight-for-height/length <i>Z</i>score: –0.75 ≤ <i>Z</i> ≤ 0.75) and the other half was moderately undernourished (–3 ≤ <i>Z</i> &lt; –2). <b><i>Results:</i></b> Structural maturational differences in the deeper dermis and subcutis regions of the skin and subtle functional changes in the epidermis were observed in moderately undernourished infants without notable clinical symptoms. Reduced skin barrier function or skin hydration were not observed in the undernourished infants, and skin pH shifted to more acidic values in this group. <b><i>Conclusion:</i></b> These findings reveal a greater impact of moderate undernutrition on the development of the dermis and subcutis and suggest that critical epidermal functions such as skin barrier and pH are mostly maintained.