Flat warts are caused by a viral infection, with HPV as the pathogen. They commonly occur on exposed areas such as the face and the backs of the hands, and are most frequently seen in adult women and children. It is necessary to strengthen immunity and provide symptomatic treatment. When necessary, physical treatments can be used to promote the disappearance of the warts, such as the commonly used methods of liquid nitrogen freezing or laser treatments. Oral administration of thymopeptide enteric capsules or pimecrolimus granules can also be used. For particularly stubborn cases, in addition to the support of traditional Chinese medicine, treatment may also need to include skin photodynamic therapy. This involves a basic treatment course of once a week for three continuous weeks, applying a photosensitizer to the affected area followed by exposure to a certain light source.