Acne is a common chronic inflammatory disease that involves the sebaceous glands of hair follicles and is cosmetically disfiguring. It can affect people of all ages, with a high incidence in young people. The development of acne is mainly related to four major causes: sebaceous gland hyperfunction, follicular sebaceous duct keratinization, Propionibacterium acnes infection, and inflammation. With concerns about the adverse effects of drug therapy (hepatotoxicity and teratogenicity), the application of these traditional treatments has been limited. For patients who cannot tolerate medication or do not want to receive medication, physical therapy is the best option, with red and blue light becoming the foundation of acne treatment. Both red and blue light are visible light, radiation-free, safe and effective. At present, acne is mainly treated clinically with simple blue light, simple red light, combined blue light and red light therapy, and red light combined with 5-ALA photodynamic therapy. 1. Blue light therapy: It is mainly used to treat mild to moderate acne. Protoporphyrin IX and fecal porphyrins are produced by Propionibacterium acnes during its own metabolism. The porphyrins absorb blue light and produce singlet oxygen and free radicals, which rapidly kill Propionibacterium acnes, while inhibiting sebaceous gland cells from secreting oil and reducing inflammatory reactions. However, the penetration depth of blue light is limited, so several consecutive treatments are required. Therefore, blue light is suitable for greasy skin, superficial inflammatory papules and pustules, while it is less effective for deeper cysts and nodules. In order to enhance the efficacy, combined treatment can also be used, such as herbal inversion combined with blue light for moderate acne. 2.Red light treatment: Mainly used for deeper acne inflammatory papules and basic treatment for post-acne skin repair. Red light penetrates deeper than blue light and can enter the dermis. In the anti-inflammatory treatment, it stimulates macrophages to release various cytokines and thus promotes the proliferation of fibroblasts to achieve the effect of skin repair, which can significantly improve skin texture and pigmentation after treatment. disorder and aggregation into clusters are somewhat improved (can treat photoaging). Although in the skin pigmentation and texture improvement on red light photodynamic significantly better than simple red light treatment, but red light treatment is painless, low cost, simple and easy to use, and more widely adapted to the population. 3. Combined treatment of blue light and red light: It can have antibacterial, anti-inflammatory and restorative effects at the same time. It has good efficacy for mild to moderate acne. Some scholars have shown that after patients received treatment twice a week for 4 weeks, the patients’ acne and inflammatory lesions were significantly reduced and the efficacy was better than using blue light alone. Each 20 minutes, 2-3 times a week, 8-10 times a course.