Skin is able to produce moisturising ingredients and has the ability to store moisture in the stratum corneum.
This requires 3 elements.
1) Natural Moisturising Factors (NMF)
2) Intercellular lipid
3) Lipid film
These 3 elements have different roles in the stratum corneum and any of them are indispensable.
When these 3 elements are sufficiently present, it maintains the ideal barrier function. Moisturising means to replenish the 3 elements to keep the skin hydrated. Among these 3 elements, NMF that is contained in corneocytes has the closest relationship with amino acids. More than 50% of NMF is made up of amino acids. This means that amino acids is one of the main source of moist skin.
The Natural Moisturising Factor (NMF), which approximately half of it is comprised of amino acids, is a “natural hydrating ingredient” inherent in the skin. It is found within the corneocytes and works to retain moisture. There are hammock-like beds made of keratin fibers within the corneocytes and the NMF is retained in these beds. However, if these hammocks are broken or if they deterioriorate, the NMF is unable to be retained within the corneocytes and is flushed out, resulting in a decrease in the volume of amino acids within the stratum corneum.