Skin is thought to be the biggest organ of the human body with a normal surface area of 1.6– 2m2 and accounts for around 15% of the total body weight of a grown-up human (Paul & Sharma, 2015). It performs numerous fundamental roles, including barrier against external physical, chemical, and biologic invaders, as well as preventing the loss of water excessively from the body and a role in thermoregulation (Kanitakis, 2002). The skin is made up of 3 layers which; from the top layer, are epidermis, dermis and subcutaneous tissue also known as hypodermis (Kanitakis, 2002) (Fig. 1.1). The external layer of skin; which is the epidermis, consist of a group of cells know as keratinocytes that synthesize keratin.