Did you know that the skin makes its own moisturiser, the natural moisturizing factor or NMF?
How the skin holds on to water
The skin has to protect the body from dehydration and from the challenges of the environment. A key part of this job falls to the stratum corneum, the outermost layer of the epidermis, which controls how much water passes through and how much is retained.
We often think of hydration as something that comes from creams. In fact the skin has its own very refined ways of keeping the right level of water, and understanding them helps us make better choices.
What the review covers
The work we are discussing is a review published in 2004. It sums up what is known about the biology of the stratum corneum, in particular the mechanisms it uses to stay hydrated.
The authors describe three main factors. The first is the lipids between the cells, arranged in highly ordered layers, which hinder the passage of water. The second is the length of the path, because water has to travel a winding route through the layers of cells. The third, just as important, is the natural moisturizing factor, known as NMF.
What NMF is
Natural moisturizing factor is a complex mix of small, water-soluble molecules. It forms inside the cells of the stratum corneum from the breakdown of a protein called filaggrin.
Every step that leads to an effective barrier, the strengthening of the cells, the processing of lipids and the production of NMF, is influenced by how hydrated the stratum corneum is. These processes, together with the final shedding of cells at the surface, are often disturbed by unfavorable environmental conditions. The result can be dry, flaky skin.
How to read this work
This review sums up the knowledge of its time and gives a clear explanation of complex mechanisms. It does not present new data, and some details have been explored further by later studies.
The practical message is that the skin actively works to hold on to water. Cold, dry air and harsh washing can disturb these processes. Gentle, consistent care helps the skin do its job. If dryness is severe or does not go away, a dermatologist can look into the cause.
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.