Components of the Skin Barrier

The skin barrier plays a critical role in maintaining skin health by preserving hydration and protecting against environmental stressors. Often described as a “brick wall,” the outermost layer of the skin, or stratum corneum, consists of corneocytes (the “bricks”) and a lipid matrix (the “mortar”) that prevents water loss and blocks irritants. A key protein in this structure is filaggrin, which breaks down into components of the natural moisturizing factor (NMF). NMF is essential for hydration and includes substances like amino acids and lactic acid. While synthetic replacements for NMF have been explored, none have truly replicated its function.

Another integral component of skin hydration is aquaporins—proteins that facilitate water transport within the skin. These channels help regulate the movement of water and maintain osmotic balance, especially in dry environments. Though not as widely discussed as lipids or filaggrin, aquaporins are increasingly recognized in skin care research for their potential to enhance moisture retention. Products that stimulate aquaporin production may contribute to a healthier, more resilient skin barrier, particularly under harsh environmental conditions.

Both internal (endogenous) and external (exogenous) stressors can disrupt the skin barrier. Environmental factors such as pollution, UV exposure, and low humidity are well-known triggers. However, lifestyle habits—including inadequate sleep, poor skin care routines, and psychological stress—also play a significant role. Many individuals unknowingly compromise their skin by using harsh products or following misguided skin care trends. The total impact of these influences is described by the term exposome, which encompasses all the oxidative and environmental challenges the skin encounters over time. Understanding and addressing these factors holistically is key to preserving skin barrier integrity and supporting long-term dermatologic health.