Skin acts as a physical barrier and provides protection against foreign invaders. Skin is characterised as primary immune system as they are considered to be a unit specialised cells of the body system. Some of these cells observe invasion by foreign proteins, like microorganism and viruses, while different cells have the capability of destroying and removing such material.
Skin is considered as the largest organ of the body which covers about 20 square feet. of human body. It includes major three layers epidermis, dermis and hypodermis.