Understanding the Skin Barrier

Dr Tara Francis provides an introduction to the skin barrier and its relevance to aesthetic practitioners

The human skin comprises three main layers: the epidermis (outermost layer), the dermis (middle layer) and the subcutaneous layer. The most upper layer of the epidermis is the stratum corneum, and is typically given a likeness to a ‘brick and mortar’ arrangement microscopically; the bricks being corneocyte cells, and the mortar being fats such as ceramides, cholesterol and fatty acids.1 The stratum corneum (SC) acts as a skin barrier and is the body’s first line of defence to the percutaneous penetration of exogenous substances, both accidentally encountered as well as deliberately (outside-inside barrier), whilst also allowing your body to retain water and other components of the body (inside-outside barrier).1,2 

The barrier to water permeation is not absolute and the normal movement of water through the SC into the atmosphere is known as transepidermal water loss (TEWL). Any changes in the cellular composition and arrangement results in altered barrier function, leading to conditions such as eczema and psoriasis, as well as symptoms such as dry skin, sensitive or inflamed skin, pigmentation, wrinkles and infection.1,2 

It’s important as medical practitioners we are educated and knowledgeable on the skin barrier function, as some patients are compromising theirs. Some of the treatments we carry out in-clinic could also be contributing to damage.