Acne is also known as “pimples”, “pimples”, “acne”, “acne”, and “acne”. “acne”. Acne is a multifactorial disease. The occurrence of acne is closely related to excessive sebum production, blockage of sebaceous ducts, bacterial infection, and inflammatory reactions. There are many treatments for acne. Oral and topical medications and physical therapy are effective for acne. With the rapid development of dermatological science in recent years, acne treatment has also made great strides, especially the rise of photodynamic therapy, which has brought a boon to the treatment of moderate to severe acne, especially refractory acne. A large amount of evidence-based medical evidence from home and abroad indicates that photodynamic therapy is one of the ideal treatments for moderate to severe acne. The mechanism of photodynamic therapy for acne is to use specific wavelengths of light to activate the porphyrins metabolized by Propionibacterium acnes, and to treat acne through phototoxic reactions, induction of cell death, and stimulation of macrophages to release cytokines and promote self-healing of lesions. It is especially suitable for the treatment of moderate to severe acne, and works mainly through four main aspects of the acne mechanism: 1. 4, by acting on the keratin forming zoo to reduce hair follicle obstruction, promote the orderly arrangement of fibroblasts and then reduce the formation of acne pits, so it can significantly restore the normal appearance of the skin and obtain satisfactory clinical effect.