After doing photodynamic therapy still have acne (medically known as acne) is a normal phenomenon, photodynamic therapy is mainly used for oncological diseases and viral warts, acne is a kind of skin follicles sebaceous glands occurring in the chronic inflammatory skin disease, clinical treatment, mainly drug therapy, but also the use of photodynamic therapy can reduce the inflammatory response, but can not stop the production of acne. Photodynamic therapy is a photosensitizer in the lesion tissue aggregation, in a specific wavelength of light or hormone irradiation is stimulated, the production of singlet oxygen or other free radicals, resulting in necrosis of the lesion tissue, the normal tissue damage is small, commonly used in the treatment of oncological diseases and viral warts, such as solar keratosis pilaris, basal cell carcinoma, etc., the use of photodynamic therapy for the treatment of acne, it can reduce its inflammatory response. It is recommended that patients should pay attention to their diet to avoid spicy and stimulating foods and sweets, keep the skin clean and hygienic, avoid skin irritation, and avoid the use of skin care products and cosmetics with high content of grease and powder to reduce the production of acne.