The whitening principles of the whitening agents involved are summarized as follows: 1, reduce the stimulation and damage to the skin by exogenous UV rays, oxygen free radicals, etc.; 2, inhibit the important enzymes in the process of melanin production, tyrosinase (the most important and most commonly used), dopa pigment isomerase, DHICA oxidase; 3, reduce melanin; 4, inhibit the transfer of melanocytes to keratinocytes; 5, accelerate the transfer of keratinocytes to keratin-forming cells, and increase metabolic renewal.