Summary: The outermost layer of the epidermis, composed of dead skin cells that form the skin’s barrier.
The stratum corneum is the top layer of the epidermis and serves as the skin’s first line of defense. It consists of flattened, non-living keratinocytes known as corneocytes, which are embedded in a lipid matrix. This layer provides a physical and chemical barrier against environmental insults, including pathogens, allergens, and moisture loss. The integrity of the stratum corneum is essential for maintaining barrier function and overall skin health.
Corneocytes are formed as keratinocytes mature and move upward through the epidermis. Eventually, they are shed in a process known as desquamation. Disruption of the stratum corneum—through over-exfoliation, harsh products, or skin conditions—can lead to increased sensitivity, dryness, and compromised barrier function.