The most likely clinical cause of a large swelling on the vulva is a cyst on the vestibular gland. When a cyst is not associated with an infection, it does not cause pain, but is only found when the vulva is cleaned daily. Most of them are caused by inflammation of the vulva or vagina, which leads to the obstruction of the vestibular gland ducts, and the fluid from the vestibular gland cannot be discharged in a timely manner, so it will be stagnated in the cystic lumen of the vestibular gland, and then the cysts will be formed gradually. Clinically, as long as you pay attention to keep the vulva clean and avoid infection, you can. Once infection occurs, local pain will occur, and in serious cases, it will lead to localized pus phenomenon, which needs to be clinically incised and drained to make the pus flow out to achieve the purpose of clinical cure.