Abstract
History reveals that cosmetics have been used since ancient days. Todays, cosmetics are used for differnt purpose with different meanings.
With the progress of science, a varieties of cosmetics having unique properties have appear on the market. Cosmetics are influenced by governments regulation, scientific technology, economical conditions and environmental problems including biological safety to human. The skin consists of epidermis layer and dermal layer which are important to cosmetics development. The thickness of the skin, excluding subcutaneous tissue, varies from 1.5 mm to 4.0 mm, It is very thin but has many protective effects.
The roles of cosmetics are to aid the functional of the skin, hair and nail as well as to make them beautify. From the considerations of the membranes, it is possible to divide the roles into treatment membrane, functinal membrane, efficacy membrane and beautifying membrane.
Treatment membrane is a cosmetics membrane that is formed by washing, cleansing and moisturizing. Functional membrane protects the skin from UV-lights. Efficacy membrane is formed by cosmetics having physiological effects. Finally, beautifying membrane is provided by cosmetics that alter appearance of the human body.
