the SC after birth using an electron microscopy isotropy (EMI) score and immunocytochemical corneodesmosomes labelling. 19 Subjects were allocated according to their age: full-term newborns (1–15 days), babies aged 5–6 weeks, babies aged 6±1 months, children aged 1–2 years, children aged 4–5 years and adults aged 20–35 years. The lowest EMI scores were noted in neonates, who together with the youngest groups of babies displayed irregular and thick cell clusters comprising poorly individualized cells versus the older groups, where a more regular distribution of superficial corneocytes was observed.19 The immunocytochemical corneodesmosome assay showed a correlation between age and structural maturation, and confirmed the relative immaturity of the epidermal barrier up to 1¬2 years after birth under basal condition. Authors concluded these findings reveal the relative immaturity of the epidermal barrier from birth to 1–2 years, which may contribute to explaining the fragility of children’s skin, its susceptibility to chemical, physical and microbial aggression and also its well-known relative permeability. Consequently, the skin of neonates, infants and young children requires special caution with topical skin care regimens.19
Studies demonstrated that certain infants with epidermal barrier breakdown at birth are predisposed to the development of AD.20-22 A randomized controlled study including 115 neonates evaluated biophysical, biological and functional properties of the developing neonatal SC from birth to 4 weeks of age.20 The study indicated the presence of impaired barrier function correlated with elevated protease activity and reduced NMF at birth and may explain the development of skin barrier dysfunction and AD.20 A cohort study showed that those with an impaired skin barrier function in early infancy and at 2 years of age demonstrated a higher risk for food allergy.22 The authors concluded that neonatal skin barrier dysfunction may predict food allergies, while skin barrier dysfunction may also support possible transcutaneous food allergen sensitization. The study showed TEWL measurements in the first few days of life may be useful in predicting AD development.22 An overview of the discussed literature is displayed in Table 1.
Prevention of Atopic Dermatitis in Babies and Toddlers Using a Moisturizer
Working with a hypothesis that improving the properties of the skin barrier early in life by applying moisturizers from birth may protect against the onset of AD in infants and early childhood, investigators developed various trials. Results from two prospective, randomized controlled trials demonstrated the daily use of a moisturizer prevented AD in 32% of Japanese and 50% of Anglo-American high-risk newborns.23,24 Horimukai and colleagues further suggested allergic sensitization during this time period is associated with the presence of AD but not with moisturizer use.24 However, a larger study may find using a moisturizer reduces allergic sensitization by preventing the development of AD.
Data from 116 infants in a randomized controlled study24 were analyzed evaluating skin barrier function measuring TEWL, stratum corneum hydration (SCH), and skin surface pH, as well as the association between skin barrier function and time-to-AD development.25 The Kaplan-Meier survival function (estimate
