Skin represents our barrier against the environment and it consists in three layers: hypodermis, the deepest layer, constituted mainly by adipose tissue, with vessels, nerves; dermis, constituted by connective tissue, with collagen and elastin fibers, blood vessels, oil glands, hair follicles, sweat glands; epidermis, the outer layer, constituted by keratinocytes which divide and mature moving from the basal layer to the stratum corneum (the outermost compartment of the epidermis). Keratinocytes, localized in the stratum corneum, feature an insoluble structure composed of several proteins called cornified envelope, cytoplasm filled by keratin filaments and nuclear dissolution. These cells are embedded into lipid layers constituted by cholesterol, fatty acids and ceramides. Stratum corneum provides skin hydration