The skin is composed of the stratum corneum at the top, the epidermis that develops underneath, its the dermis layer under this. There are 16 layers (corneosit) in the stratum corneum. Lipids (cholesterol, fatty acids, ceramides) are secreted into the spaces between the corneocytes from the lamella cells to form a regular cell and fat structure. These oils provide water flow between cells. The epidermis continually regenerates the stratum corneum while exogenous cells exfoliate. When stratum corneum is cracked, the first defense cells are Langerhans cells. The stratum corneum layer acts as a barrier that protects the skin against bacteria, irritants, allergens and external effects.

Stratum corneum develops rapidly after birth, but it takes weeks to months to fully mature. For the flexibility of the outer layer of the skin during movement and to prevent the cracking and exfoliation, moisturizing the stratum corneum is essential.