Flat warts are a skin disease caused by human papillomavirus infection, which can be transmitted through direct or indirect contact, and the virus can cause abnormal proliferation of epithelial cells through broken skin. Flat warts are one of the most common viral skin diseases caused by HPV virus infection. Flat warts are contagious and can be transmitted to others through direct or indirect contact with the affected area, sharing towels and personal items with the patient. Patients can also scratch the affected area to bring the virus to other normal skin and self-infection, for immunocompromised and traumatized patients are more likely to be infected. For those who have flat warts, it is recommended to go to a regular hospital for examination and standardized treatment under the guidance of a professional doctor.