ABSTRACT
Dry skin symptoms are frequently linked to an impaired skin barrier function, as observed in psoriasis, ichtyosis, atopic skin, and contact eczemas.1 More precisely, this skin barrier function is connected to the chemical and physical condition of the stratum corneum (SC), the uppermost layer of the epidermis. SC gives protection against desiccation and environmental challenge by regulating water flux and retention.2 The optimal level of hydration maintained in SC is largely dependent on three components, which are constantly regenerated in this particular skin layer, namely (1) intercellular lamellar lipids, as an effective barrier to the passage of water; (2) corneocytes (SC cells), which provide the tortuous diffusion path, created by the SC layers and corneocyte envelopes, that retard water loss, and (3) natural moisturizing factor (NMF), a complex mixture of low-molecular-weight, water-soluble compounds first formed within the corneocytes by degradation of the histidine-rich protein known as filaggrin. Disturbance to the regeneration processes of these components results in dry, flaky skin conditions.3
