membrane inhibits water evaporation, which is essential for terrestrial life (Figure 2).9-11
The Vernix caseosa also protects the immature barrier function of neonatal skin (Figure 3).11,12 Previously, removed entirely after birth; it is now often allowed to separate over six hours to five days after birth naturally.12 The vernix layer increases hydration, suppleness, and plasticity of the SC.3,11,12 This protective layer decreases skin surface pH, inhibiting pathological bacteria growth, and facilitates commensal growth.3,11-13 The main component of vernix caseosa is water, which is much higher than the water content of some barrier creams, such as those that lack humectants mimicking natural moisturizer factors (NMF).11-14 The lipid content of vernix caseosa is comprised of cholesterol (52.8%), free fatty acids (27.7%) and ceramides (20.1%).11
Research of the past ten years has shown that at birth, neonatal skin is structurally and functionally immature compared to adult skin.4,7-10 The skin of neonates and infants is considered as a fragile physiological skin, with lower resistance to aggressions, eg, microbes and has an elevated skin surface pH.1,2,15,16 The pH of the neonatal skin surface is typically more alkaline than mature skin, ranging from 6.34 to 7.5, depending on the anatomical site.1,2,4,5 Several mechanisms may play a role in elevated skin pH at birth; the most relevant could be the exposure to the alkaline amniotic fluid during the preborn life.1,2,4,5
A slightly acidic skin surface pH or “acid mantle” defends the skin against infection, influencing the composition of cutaneous bacterial flora.4 The process of skin acidification plays an important role in barrier maturation and the activation of enzymes involved in the extracellular processing of stratum corneum lipids. 4,5,7-10
Statement 2: The complete maturation process of neonatal skin takes from two to four (2–4) years.
Studies on the physiological maturation process of neonatal skin revealed that dynamic changes in the NMF content take place during infancy, with the lowest amount present at six months of age.8-11 An in-vivo study on full-term newborns (1–15 days), infants (5–6 weeks and six months), children (1–2 years and 4–5