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It has been 15 years since Rawlings published the first research paper on stratum corneum moisturization at the molecular level, elucidating the structure and function of the stratum corneum. The paper reviewed the then-understanding of the stratum corneum biology; focusing on the protective function of skin against desiccation and environmental challenge by regulating water flux and retention. It postulated three factors that maintain homeostasis of hydration:
- Intercellular lamellar lipids, organized predominantly in an orthorhombic gel phase, provide an effective barrier to the passage of water through the tissue.
- The diffusion path length also retards water loss, since water must traverse the tortuous path created by the SC layers and corneocyte envelopes.
- The natural moisturizing factor (NMF); a complex mixture of low molecular weight, water-soluble compounds, first formed within the corneocytes by degradation of the protein filaggrin.
The paper described how each maturation step that leads to the formation of an effective moisture barrier (including corneocyte strengthening, lipid processing and NMF generation), is influenced by the level of stratum corneum hydration. Rawlings stated that these processes, as well as the final step of corneodesmolysis that mediates exfoliation, are often disturbed in response to environmental challenges, resulting in dry, flaky skin conditions.1
Research has since built upon—and progressed significantly from—the principles Rawlings proposed. However, dry skin remains a frequent complaint.
Adult Xerosis: Prevalence and Treatment
Dry skin is a multifaceted condition that may be associated with skin irritation, itch and discomfort, which can eventually manifest as skin disease.2 As an example of its prevalence, 29.4% of more than 48,000 German adults were found to have xerotic skin after a whole-body assessment. Older age, but not gender, was associated with dry skin.
Xerosis is also a significant predictor for atopic eczema, psoriasis and seborrhoeic dermatitis, demonstrating that dry skin requires attention prior to deteriorating into skin disease. There are many approaches to improving skin hydration, including hydrating ingredients and formulations designed for effective delivery. These may include nanocarriers or skin regeneration technologies using cells that have shown great promise for skin moisturization.3
The inside-out approach is an alternative.
Continue reading in the Nov./Dec. 2019 digital magazine...