4.1.1　The concept of skin protection

With the development of human society and the advancement of science and technology，the environment that we face is becoming more and more complex.In the process of production，there are many factors that can cause harm to the skin，which can be summarized as physical factors，such as radiation，electricity，light，heat，and mechanical friction；chemical factors，such as petroleum fractionation products，strong acids，strong bases，heavy metals，and asbestos；biological factors，such as bacteria，fungi，viruses，insect bites，and pollen.Therefore，it is very important to carry out personal skin protection against these physical，chemical and biological factors that endanger skin health in production and life.(https://www.daowen.com)