Adult women's vagina is a weakly acidic environment, the vaginal pH is about 3.8 ~ 4.5, which is conducive to killing various pathogenic bacteria and conditionally pathogenic bacteria that enter the vagina. However, when the local microenvironment of the vagina changes, the microbial flora growth and reproduction and vaginitis, common trichomonas vaginitis, candida vaginitis and bacterial vaginitis. Trichomonas is unfavorable in the normal vaginal environment, and is most active in the PH5.6-6.0 environment. Therefore, even if Trichomonas enters the vaginal environment below PH 5.0, it is difficult for it to grow and reproduce. Only when the vaginal pH rises can Trichomonas multiply and grow rapidly, causing vaginitis. Candida is one of the normal flora of the human body and is widely found on human skin, oral cavity and genital mucosa. About 10% of healthy women and 30% of pregnant women are healthy carriers without any clinical symptoms, so it can be seen that in the normal environment of the reproductive tract, Candida will not cause disease. Only when the PH value rises to about 5.5, the growth and reproduction is most active and can cause disease. Bacterial vaginitis is a mixed infection caused by a decrease in Lactobacillus in the vagina and the proliferation of Gartnerella and anaerobes. In bacterial vaginitis, the pH can be 5.0 to 5.5 or higher. Semen, which is alkaline, produces and releases free amines in the presence of anaerobic bacteria, which is the reason for the increased ichthyosis after intercourse in patients with bacterial vaginitis. It can be seen that whether or not vaginitis occurs, in addition to the body resistance, sex hormone levels, but also with the vaginal microenvironment in the PH value changes have a close relationship. Under normal circumstances, the vagina has a natural self-cleaning and regulating ability to maintain the relative constancy of the local microenvironment, which is conducive to reproductive health. The frequency of sex may have a certain impact on women's health, this is because the PH value of semen in the 7.2 ~ 8.0, after sex alkaline semen in a short period of time can neutralize the vagina weak acidic environment. When sex is too frequent, it may affect the vaginal local micro-environmental changes, coupled with the excessive use of neutral detergents by some women to douche the vagina, so that the vaginal environment is further damaged, conducive to the propagation of microorganisms and cause disease. From the above said basically 4.5 or so, 5.0 or more is at least vaginitis To submit a report, the normal situation is certainly 3.8 ~ 4.5 , I am studying medicine