The pH of a normal female vagina is less than 4.5, usually between 3.8 and 4.4. This pH gives the vagina an acidic environment and prevents the growth of bacteria that prefer to grow in a weakly alkaline environment. Due to the large number of Lactobacillus bacteria inside the vagina, it is able to break down the glycogen in the vaginal wall into lactic acid, thus acting as an acidic agent. When the pH level is 5.1, it means that the vagina is less acidic and this time it is easy for other bacteria to grow and multiply inside the vagina and this will lead to a decrease in the defensive function of the vagina, so special attention should be paid to the presence of pH 5.1 to prevent other bacteria from causing vaginal inflammation.