A hard lump on the labia may be caused by vestibular cysts, boils and vulvar cysts. 1. Vestibular cysts: Commonly found on the labia majora and minora, local skin cysts of varying sizes, mostly oval in shape. The cause may be congenital narrowing of the gland ducts, vestibular adenitis and other factors. 2. Boils: the cause of its formation is mostly related to Staphylococcus aureus, scratching the skin, trauma may also induce the disease. The main symptom is one or more red nodules, which may be swollen and painful, and the disease can occur in any part of the body. 3. Vulvar cyst: its cause may be related to the blockage of the vulvar secretory gland ducts, trauma and tissue development, etc. Patients will have single or multiple painless lumps locally. There are many diseases that can cause a hard bag to grow on the side of the labia, and it is recommended that patients seek medical examination to clarify the cause of the disease.