Skin, the largest organ, is a complex cellular system that serves many functions. It is made up of two layers: the dermis and epidermis (and the subcutaneous tissue, which functions as the connective layer). In addition to thermal regulation, the skin also moderates fluid balance, acts to protect underlying structures, and serves as a sensory and physical link to the outside environment. Water is essential to normal homeostatic regulation. The stratum corneum, the outermost layer of the epidermis, functions to maintain this delicate process as well as providing an external barrier to outside insults, such as bacteria. Tightly packed corneocytes, along with intercellular lipids found in the epidermis function to prevent water loss and serve as a barrier to potentially hazardous materials entering the body. If the skin barrier is disrupted, water loss occurs and bacterial invasion can occur .