Acne is a common chronic inflammatory skin disease involving the sebaceous glands of hair follicles. It occurs mostly on the face of young people and leaves pigmentation or scars after healing. Traditional treatments for acne include oral tetracycline antibiotics, retinoids, and birth control pills. However, oral medications have a long course of treatment and have large systemic toxic side effects. Therefore, a new effective topical treatment method with fewer adverse effects is needed. Photodynamic therapy is an emerging treatment technology that has been widely used in dermatology in recent years, and can be used to treat acne, condyloma, skin tumors, and bright red nevus. For acne, it is most effective for moderate to severe acne of inflammatory papules, pustules, and nodular cysts. It is also quite effective for acne, and there are a lot of research results showing that the number of acne will be significantly reduced after photodynamic treatment. The principle of action is that the photosensitizer 5-aminoketovaleric acid is applied topically to the acne area. The photosensitizer is absorbed by the sebaceous glands and converted to porphyrin IX, and then irradiated with specific wavelengths of light to stimulate the production of monomorphic oxygen to kill cells, while destroying the sebaceous glands and reducing sebum secretion to achieve the purpose of eliminating acne. Operation steps: 1. Take pictures and keep files. 2. Apply topical photosensitizer: 5-aminoketovaleric acid (5-ALA) to the acne area. 3. Rest for 3-4 hours and then apply specific wavelengths of light (blue/red light). 4. 1-2 weeks treatment session for 1-3 sessions. Photodynamic therapy is more effective, there will be a transient pain during the treatment process, but overall the side effects are small, mainly local redness and burning after surgery, which can subside on its own, or can be solved by cold compresses. Individual patients with darker facial skin will have temporary hyperpigmentation, but it will subside on its own. To avoid hyperpigmentation, it is recommended to avoid bright light exposure, such as fluorescent lights, for at least 2 days after treatment, in addition to avoiding prolonged exposure to computers and TVs, which is more effective if combined with the use of restorative masks. Photodynamic therapy is a new acne treatment device with the characteristics of rapid elimination of acne, no scarring, and no systemic toxic side effects.