There are many reasons for the redness and swelling of the vaginal opening. 1. The vulva is easily stimulated by vaginal secretions from menstrual blood, if you don’t pay attention to cleaning at this time it will cause swelling and pain at the vaginal opening, sometimes there is also itching and burning sensation of the mucous membrane of the vulvar skin, it is recommended to go to the hospital for examination of vaginal secretions to determine the pathogen and then treat it. 2. It is recommended to keep the perineum clean and dry, wear breathable underwear and buy good quality sanitary napkins.