Skin is the body's largest organ. It protects us from external factors. It is made up of three layers: the epidermis, the dermis, and hypodermis. The main purposes of skin are sensing, regulating, and protecting. The epidermis (the topmost layer of the skin) is composed of mostly of keratinocytes, these are entirely replaced every 4 weeks in a process called cellular turnover. New cells formed at the base of the epidermis and push older ones up. As the new cells are pushed up, they gain keratin (a hardened protein) and eventually they die. The dead skin cells form a tightly packed waterproof layer and eventually shed off in a process called desquamation.

 

Microorganisms inhabit the skin, including fungi and bacteria, these thrive in the sebum- the skins natural oil. Cells are held together by a layer of oil (lipid) in healthy skin press tightly together to form a barrier (which prevents dehydration). 

Drops in lipid production result in water being lost from the cells causing them to shrink and crack leaving gaps. Irritants can penetrate these gaps resulting in skin concerns such as redness and irritation.