A child’s skin is not a miniature version of an adult’s: it is an organ in active development, whose structures and functions gradually take shape over the years. From birth to around age six, the skin barrier strengthens, cells renew rapidly, and the microbiome slowly stabilizes. These transformations, both microscopic and visible, mold the skin to prepare it for its role: protecting the body from the external environment.
In the newborn, the skin is thin, permeable, and particularly vulnerable to environmental insults. The stratum corneum consists of loosely packed lipids and small corneocytes, which makes the skin barrier less effective than in adults. As a result, water loss through the skin is higher, explaining infants’ tendency to have dry skin. As they grow, the skin becomes thicker and more resilient. By about six years of age, stratum corneum thickness, water loss, and corneocyte size reach levels comparable to those in adults.
Furthermore, during early childhood, cellular metabolism remains high due to the rapid proliferation of keratinocytes. Likewise, melanocyte activity—the cells that produce melanin—gradually increases. Children’s complexions become slightly darker, while the skin thickens and gains resistance to UV radiation. However, this developing skin remains highly sensitive to sunlight. The process of melanogenesis is not yet optimal and the free radical defense mechanisms are immature. This is why it is very important not to expose the children to the sun.
Finally, theskin's microbial ecosystem also undergoes a gradual evolution. In infants and young children, bacteria of the phylum Firmicutes dominate the skin flora, whereas in adults, it is mainly the Proteobacteria and the Actinobacteria that predominate. Microbial diversity increases and gradually stabilizes, allowing immunity to strengthen.