Oral sex does not usually affect menstruation, but it may cause inflammation of the reproductive tract or infection with sexually transmitted diseases, etc. First of all, there are many reasons for irregular menstruation, such as a thin uterine lining, endocrine disorders, and the use of certain medications, but they are usually not related to oral sex. Secondly, oral sex may cause bacterial vaginitis. The flora in the oral cavity is different from the flora in the reproductive system. Oral sex is easy to cause dysfunction of the flora in the vagina, so that the biological barrier in the vagina is damaged, which leads to the occurrence of gynecological inflammation such as bacterial vaginitis, but this will not affect the menstrual situation. In addition, oral sex can also lead to the spread of sexually transmitted diseases (STDs) if the other person has an STD, and it is highly likely that an infection will be caused by oral sex. Therefore, frequent oral sex is not recommended. Women, in particular, should pay attention to personal hygiene in daily life and try to keep the vulva clean and dry to maintain the health of the reproductive tract.