From the current understanding of the compositional changes in dry skin five aspects of stratum corneum lipid biochemistry need to be corrected: The lowered levels of ceramides generally. The phytosphingosine-containing ceramide insufficiency. The ceramide one linoleate (CEOS) insufficiency. The lowered covalently bound ceramides. The precise chain length of the ceramide sphingoid bases and free fatty […]

Although a major analysis of dry skin treatments are outside of the scope of this review it is worth mentioning just briefly the biology that needs to be corrected in cosmetic dry skin conditions and some key examples of suitable treatments. Traditionally, humectants, occlusives, and emollients have been, and will continue to be, the mainstay […]

Classically, dry skin has been described in two ways—(1) as a condition that is simply either present or not or (2) as a linear progression of sequelae, resulting in the concomitant development of clinical tools such as linear visual grading scales, etc. While not refuting the validity of these, it is proposed that the induction […]

The differences in SC water concentration profiles between normal and dry skin influence the enzymic reactions in the SC. In dry flaky skin conditions, corneodesmosomes are not Externally approximately months conditioning 78%RH and 24 C Figure 15 Time course of TEWL adaptation in humans working in an ultra-low humidity environment (1.5%RH). Source: From Ref. 67. […]

Before considering the biology of dry skin and the dry skin cycle, it is important to review the effect of environmental conditions on the SC, as these are the primary initiating events for the precipitation of the condition. In studies conducted in the different seasons of the year in the U. K., Rogers et al. […]

A historical perspective on filaggrin biology was given by Rawlings et al. (1). Biologically, NMF allows the outermost layers of the SC to retain moisture against the Figure 11 Double staining of CEs with Nile red and anti-involucrin (shown here in gray scale). (A) Face and (B) upper arm. Source: From Ref. 51. desiccating action […]

The CE is an extremely stable and insoluble proteinaceous layered structure. The stability of the envelope is attributed to the degree of cross-linking of envelope proteins by either disulphide, glutamyl-lysine isodipeptide bonds, or glutamyl polyamine cross-linking of glutamine residues of several CE proteins (44). The enzymes, responsible for catalysing the gamma-glutamyl-epsilon-lysine isodipeptide bond formation, are […]

The “brick and mortar” model of the SC has been known for many years. However, a more complete description of this model includes “corneodesmosomes.” Corneodesmosomes (26) are macromolecular glycoprotein complexes incorporated into the CE and consist of the cadherin family of transmembrane glycoproteins, desmoglein 1 (Dsg 1) and desmocollin 1 (Dsc 1). These glycoproteins span […]

All SC lipids are important for barrier function of the skin but due to their unique properties and structure the ceramides have been of most interest in recent years. Ceramides constitute (on a weight basis) approximately 47% of the SC lipids (14). Given this diversity, together with the identification of new ceramides, a new nomenclature […]