Too much time for sex does not usually cause vaginitis, but not doing a good job of vaginal hygiene before sex may cause vaginitis. If both parties do not do a good job of pubic hygiene before sex, women’s clitoris, labia majora and minora, perineum, anus and other parts of the male glans, penis foreskin and other parts of the glans may have a large number of bacteria and other pathogens, even if the sex time is relatively short, the pathogens may be brought into the vagina to cause vaginitis. If before sex, both sides do a good job of pubic hygiene, even if the sex time is longer, generally does not cause vaginitis. The length of sexual intercourse is not directly related to whether or not it causes vaginitis, but is directly related to whether or not it is good vaginal hygiene. Both parties must keep the pubic area clean before sexual intercourse, and avoid sexual intercourse during menstruation, pregnancy, and urinary system diseases. Women who suffer from vaginitis and other gynecological inflammation after sex should go to the regular hospital in time, under the guidance of the doctor, so as not to affect the health of the body.