Barrier Function and Water-Holding and Transport Properties of Infant Stratum Corneum Are Different from Adult and Continue to Develop through the First Year of Life  Janeta Nikolovski, Georgios N. Stamatas, Nikiforos Kollias, Benjamin C. Wiegand  Journal of Investigative Dermatology  Volume 128, Issue 7, Pages 1728-1736 (July 2008) DOI: 10.1038/sj.jid.5701239 Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Skin conductance is higher in infants. (a) Age distribution of skin conductance measurements (a.u.=arbitrary units) on the ventral side of the upper arm. (b) Data taken from the upper ventral arm were grouped by age: 3–6 months (N=21), 7–12 months (N=46), 13–48 months (N=17), and adults (N=71). Skin conductance values of the upper ventral arm decrease after the first 12 months of life (*P<0.0005, 3–12 months vs adult). (c) Data taken from the lower dorsal arm were averaged similarly. Skin conductance values of the lower dorsal arm decrease after the first 12 months (*P<0.0005, 3–12 months vs adult). Data shown as mean±SD. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 Water content of the infant SC is higher than that of the adult SC. (a) The average distribution of water on the lower ventral arms of infants (aged 3–33 months, N=13) and adults (N=13) was measured within the top 40μm of the skin by Raman confocal microspectroscopy. Infant SC contains more water than adult SC (*P<0.05 up through the first 26μm). Data shown as mean±SD. (b) The water distribution within infant SC demonstrates a steeper slope (at depths of 4–14μm). Data shown as mean±SD, *P<0.005. (c) Infant SC contains higher concentration of water within the top 20μm than adult SC, calculated by the area under the curve (AUC). Data shown as mean±SD, *P<0.0005. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 TEWL values are higher in infants. (a) TEWL from the upper ventral arm for each subject was measured and plotted against age. (b) Data taken from the upper ventral arm were averaged for infants ranging in age from 3 to 6 months (N=19), 7 to 12 months (N=31), and adults (N=71). TEWL values from the upper ventral arm are higher for the first 12 months of life compared to adult (*P<0.0005 for both age ranges). (c) Data taken from the lower dorsal arm were averaged similarly. TEWL values from the lower dorsal arm are higher in the youngest subjects (*P<0.01, 3–6 vs 7–12 months) and higher among all infants tested than that of adults (*P<0.0005, 3–6, 7–12 months vs adult). Data shown as mean±SD. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 Exogenous water absorption and desorption rates are higher in infants. The absorption and subsequent desorption of exogenously applied water was monitored by measuring skin conductance before and 10seconds after water application to the skin of the lower dorsal arm. (a) Infant skin (N=88) shows a higher change in conductance values from baseline than adult skin (N=97; *P<0.001 at 30seconds). (b) Rates of change were calculated and averaged from initial to maximum value (rate of absorption) and from maximum to the value at 60seconds (rate of desorption). Infant skin demonstrates a higher rate of water absorption (*P<0.002) and desorption (*P<0.0001) than adult skin. Data shown as mean±SD. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 Water absorption profiles. The absorption of exogenously applied water was monitored by in vivo Raman confocal microspectroscopy 10seconds after water application to the skin of the lower ventral arm. Data were averaged before and after water application. (a) A significant amount of water absorption was found within the SC of infants less than 12 months old (N=5; *P<0.05 before vs after for first 8μm). (b) In contrast, no significant water absorption was found in adult skin (N=7) after water application. Data shown as mean±SD. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 6 NMF concentration is lower in infants. The average distribution of NMF on the lower ventral arms of infants (aged 3–12 months, N=8) and adults (N=15) was measured within the top 28μm of the skin. Infants have less NMF in the SC and upper epidermis of their arms as compared to adults (*P<0.05 up through the first 12μm). Data shown as mean±SD. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 7 A combination graph (TEWL vs conductance) demonstrates the differences in water-handling properties of infant SC vs adult SC. TEWL and conductance values from the upper ventral arm for each subject were measured and plotted against each other. The graph demonstrates the high variability of the state of the infant SC (being in a “state of flux”) compared to the well-established water-handling control mechanisms of adult SC. Journal of Investigative Dermatology 2008 128, 1728-1736DOI: (10.1038/sj.jid.5701239) Copyright © 2008 The Society for Investigative Dermatology, Inc Terms and Conditions