Skin is the outermost layer of the human body which regulates the body temperature and protects the body from abrasion and water loss. The Young's Modulus of skin is measured as a ratio of the stress applied to the skin in vitro or in vivo over the skin deformation. Skin is found to be highly anisotropic and Young's Modulus is found to be dependent on orientation with respect to Langer's lines, where highest value is seen in the parallel orientation, and can be twice the perpendicular values. Young's Modulus decreases up to three orders of magnitude with hydration. An inverse relationship between skin's thickness and Young's Modulus is observed. It can be concluded that the thickness of skin increases with age until 30 years and varies inversely with age after then. This paper summarises evidence for correlation of Young's Modulus with intramural and extraneous factors such as Langer's lines, skin's thickness, ageing and hydration.