What is the vaginal pH value of normal adult women?

The vagina of adult women is in a weak acid environment, and the pH value in the vagina is about 3.8 ~ 4.5, which is beneficial to kill all kinds of pathogenic bacteria and conditional pathogenic bacteria entering the vagina. However, when the local microenvironment of vagina changes, microbial flora grows and reproduces, resulting in vaginitis, such as trichomonal vaginitis, candidal vaginitis, bacterial vaginitis and so on. Trichomonas is not conducive to growth in normal vaginal environment, and is most active at pH 5.6 ~ 6.0. Therefore, even if trichomonas enters the vaginal environment below PH5.0, it is difficult to grow and reproduce. Only when the PH value of vagina increases can trichomonas multiply and grow rapidly, causing vaginitis. Candida is one of the normal flora of human body, which widely exists in human skin, oral cavity and genital mucosa. About 10% of healthy women and 30% of pregnant women are healthy carriers without any clinical symptoms, indicating that Candida will not cause disease in normal reproductive environment. Only when the PH value rises to about 5.5 can the growth and reproduction be the most active and cause disease. Bacterial vaginitis is a mixed infection caused by the decrease of lactobacillus in vagina and the reproduction of Gardnerella and anaerobic bacteria. Bacterial vaginitis, the PH value can reach 5.0 ~ 5.5 or higher. Semen is alkaline, and free amine is produced and released under the action of anaerobic bacteria, which is the reason why the fishy smell of patients with bacterial vaginitis increases after sexual intercourse. It can be seen that whether vaginitis occurs is not only related to the body's resistance and sex hormone level, but also closely related to the change of PH value of vaginal microenvironment. Under normal circumstances, vagina has natural self-purification and regulation ability, and keeping local microenvironment relatively constant is beneficial to reproductive health. The frequency of sexual life may have some influence on women's health, because the PH value of semen is 7.2 ~ 8.0, and alkaline semen after sexual life can neutralize the weak acidic environment of vagina in a short time. When sexual life is too frequent, it may affect the changes of local microenvironment of vagina. Some women overuse neutral cleaning agents to rinse vagina, which further damages the vaginal environment and is conducive to microbial reproduction and disease. From what I said above, it is basically around 4.5. If it is above 5.0, it is at least vaginitis. I have to submit a report. The normal situation must be 3.8 ~ 4.5. I am studying medicine.