Red and blue light therapy instruments are used to treat acne, commonly known as pimples, and are divided into red light and blue light. Red light has a longer wavelength and can penetrate deeper into the skin tissue, killing Propionibacterium acnes to a certain extent, as well as promoting skin collagen fiber renewal, promoting cell growth and skin repair. Blue light has a shorter wavelength and penetrates shallower than red light. The killing effect of blue light on Propionibacterium acnes is stronger than that of red light, and its main function is to sterilize and reduce inflammation, and to a certain extent it can reduce sebaceous secretion. The combination of red and blue light is more effective for acne treatment, with 2-3 times a week exposure. These two types of light are relatively mild and there are no adverse reactions. After treatment, attention should be paid to strict sun protection. The role of red light and blue light therapy device is summarized in three aspects: sterilization, anti-inflammation and repair.