What Is Stratum Corneum?
What It Is
The stratum corneum is the outermost layer of the epidermis. The source describes it as a structure of flattened, keratinised cells held together by lipids and commonly explains its organisation using a “brick and mortar” model.
What It Does
The stratum corneum forms the primary physical barrier against excessive water loss and entry of irritants. Its condition therefore has a direct relationship with skin hydration and tolerance.
How It Functions in a Formulation
The stratum corneum is not a formulation ingredient. It is the main skin layer discussed when evaluating the effects of bathing, cleansing, moisturising and other topical products on barrier function.
Safety and Tolerance
The source identifies very hot water, harsh surfactants and over-exfoliation as factors that can compromise the barrier. A compromised stratum corneum can increase water loss and make skin more reactive.
What the Source Supports
The source supports the stratum corneum as the skin's principal outer barrier and as an important concept for understanding bathing-related changes in hydration, irritation and barrier function.