The skin is the outermost covering of living tissue. It is the largest organ of the body and it is made up of multiple layers of epithelial tissues to guard the underlying muscles, bones, ligaments and internal organs. The skin contains various functional systems and cell types to provide comprehensive protection against external elements and as such, it is excessively exposed to harsh and damaging environmental aggressions including sunlight (UV exposure), free radicals and other hazardous molecules that lead to the expression of wrinkles and pigmentation (age spots), loss of elasticity and flexibility, and higher susceptibility to the buildup of damage.
Skin is composed primarily of the epidermis and the dermis. The outermost epidermis is made up of stratified squamous epithelium with an underlying basement membrane. It contains no blood vessels and is nourished by diffusion from the dermis. The epidermis is composed mainly of keratinocytes with melanocytes as well as langerhans cells. This layer of skin functions as a barrier between the body and the external environment, maintaining water inside the body and keeping out harmful chemicals and pathogens.1