There are several reasons for the swelling and pain of the vaginal opening: 1, whether there is local damage to the vaginal opening, such as cycling or improper exercise, resulting in local soft tissue damage to the perineum; 2, allergy to underwear, sanitary napkins, washing supplies, some women are more sensitive and prone to allergies, which can also produce swelling and pain in the vaginal opening; 3, if swelling and pain is more intense, and to exclude the above factors, it may be vaginismus, which produces redness, swelling, and pain in the vaginal opening.