Vaginal pH refers to the acidity and alkalinity of a woman’s vagina. The normal female pH is less than or equal to 4.5, mostly between 3.8 and 4.4, and is the result of the combined action of estrogen and lactobacilli. Under physiological conditions, estrogen in a woman’s body can make the vaginal epithelium proliferate and thicken, and lactobacilli in the vagina can convert simple sugars in the vagina into lactic acid, thus maintaining a normal acidic environment in the vagina, which can inhibit other bacteria from growing and reproducing in it. If the pH level of the vagina increases, other bacteria can easily grow and multiply in it. If women like vaginal douching or have frequent sex, the pH level of the vagina will rise, which is not conducive to the growth of lactobacilli, making it easy to have vaginal inflammation.