One of the most interesting aspects of the cells that make up the surface of the skin is their multi-functionality. While mostly known for their protective barrier properties, the living beings colloquially known as “skin cells” (and more technically as “keratinocytes” in honor of their most prolific extrusion, the fingernail like protein called keratin) are much more than a cellular shield. “Skin cells” are biochemical dynamos, each one producing, secreting and becoming ultimately a wide range of very functional chemicals.

“Skin cells” make vitamin D, they produce prodigious quantities of skin fats (lipids), and they are also the source of many hormone chemicals. Some, like cortisol, are involved in obvious skin functions like protection. Others, like the nervous system's serotonin and dopamine, make the skin a type of brain appendage. Not to forget pheromones, which are involved in less obvious skin functions, like signaling, sexual attraction and fertility.