The vagina is home to a variety of pathogens (including bacteria) that form a normal vaginal microbiota. Although a variety of bacteria are present in the vagina, they do not cause disease because of the ecological balance between the vagina and these flora. Lactobacillus, estrogen and vaginal pH play an important role in maintaining the ecological balance of the vagina. The reproductive tract of normal women of reproductive age has natural defense mechanisms. The microecology of the vagina is dominated by Lactobacillus vaginalis. Under the influence of estrogen, the vaginal epithelium is constantly proliferating and rich in glycogen, which is broken down into lactic acid with the help of Lactobacillus vaginalis, maintaining a vaginal pH of 4-5 and effectively killing pathogenic bacteria or inhibiting their reproduction. When the ecological balance of the vagina is disturbed or when exogenous pathogens invade, inflammation can occur. A decrease in estrogen or an increase in vaginal pH, such as frequent sexual intercourse or vaginal irrigation, can elevate the vagina, which is not conducive to the growth of Lactobacillus. Long-term application of antibiotics to inhibit the growth of Lactobacillus can cause other pathogenic bacteria to become dominant and cause inflammation.