Did you know that the outermost layer of the skin, the one you apply cream to, carries out several linked defensive functions?
More than a barrier
When we apply a cream, the first thing it meets is the stratum corneum, the outermost part of the epidermis. It is a very thin layer, made of cells that have lost their nucleus, embedded in a matrix of lipids. It looks like an inert surface, yet it is a very active tissue.
When we talk about barrier function, we usually mean control of water loss. That is its most important job, but the stratum corneum also performs many other defensive tasks against the outside world.
What the review covers
The work we are discussing is a review published in 2005 in the Journal of Investigative Dermatology. The author proposes looking at the defenses of the skin in an integrated way, since most of the skin’s protective functions are located in the stratum corneum.
The review explores how the different defensive functions are connected, how they are regulated together in response to specific stresses, and how a change in one function affects the others. It then describes the structural and biochemical basis of these defenses.
The main point
The defensive functions of the stratum corneum are linked because they share the same location or common biochemical processes. When the skin is under stress, these functions respond in a coordinated way.
The consequence is important. If one of the functions is disrupted, the others are affected too. In the same way, supporting the skin barrier means supporting a system of defenses that work together. The author also discusses the clinical consequences of this view and its possible applications in treatment.
How to read this work
This is a theoretical review, useful for building an overall picture from many studies. It does not present a new experiment, and its practical implications should be read as directions for research and care.
The message for your daily routine is that the skin works as a system. Harsh cleansing, too many products or sudden changes in climate can weaken several defenses at once. Protecting the stratum corneum with gentle, consistent habits is a good place to start. If your skin stays dry, red or irritated, see a dermatologist.
This article is for information only. It does not replace the advice of a doctor or dermatologist, whom you should consult with any question about your skin.