Dry skin can result from the loss of natural moisturizing factors and subsequent damage to the skin's moisture barrier, triggering the release of substances within the skin that cause irritation and itch. The subsequent scratching can damage the moisture barrier, leading to extremely dry, itchy skin.
The free amino acids, along with other physiological chemicals such as lactic acid, urea and salts, are present in the stratum corneum.
- Together these elements are called 'natural moisturizing factors' and are responsible for keeping the skin moist and pliable by attracting and holding watera property called hygroscopic. Better results can be achieved with the help of a good skin moisturizing product.
- The water content of the stratum corneum is normally about 30%. Filaggrin is decomposed into amino acids only when skin dryness is present to regulate how much water it holds. Therefore, this breakdown is more frequent in dry weather areas.
Generation of Natural Moisturizing Factors in the Skin
1) Maturation and differentiation of epidermal cells in the second layer of skin
2) Filaggrin protein clumps into granules in the granular cell layer
3) Filaggrin becomes complexed to keratin protein to protect from proteolytic degradation.
4) Dermal cells are transformed into corneocytes, getting emptied and filled with keratin/filaggrin proteins
5) Corneocytes move towards the very outer layer skin
6) The keratin/filaggrin complex is enzimatically broken
7) Stratum corneum loses water
8) Proteolytic enzymes activated
9) Filaggrin degraded into individual amino acids
10) Amino acids plus other chemicals form Natural Moisturizing Factors in stratum corneum
11) Holds water to rehydrate stratum corneum; this can be enhanced using a skin moisturizer
Desquamation (The Shedding of Skin Cells)
Desquamation is another great help in keeping the skin smooth.
- Desquamation involves the enzymatic dissolving of the desmosomes, the protein connections that keeps corneocytes together, and the eventual elimination of these cells.
- Opposite to the production of amino acids from proteolytic reduction of filaggrin proteins, the proteolytic enzymes responsible for desquamation function in the presence of a well-hydrated stratum corneum. These enzymes are located intercellularly. Cells do not desquamate normally in a dry ambience, and the result is thickened, scaly, rough, dry skin.
- Production and shedding of corneocytes are physiologically balanced. Increased production of corneocytes (skin diseases like psoriasis) or decreased shedding (skin diseases like ichthyosis) produces an aggregation of cells on the dermal surface and dry, rough skin.
Desquamation of Cells
1) Intact corneocytes in upper layer of hydrated stratum corneum
2) Protein connections between corneocytes are enzimatically broken
3) Corneocytes desquamate. After that, skin stays healthy with no dry scales
