pH test strips are used to measure the activity of hydrogen ions in a solution, which directly determines the acidity, neutrality and alkalinity of the solution, so pH test strips can help women to check the pH level in the vagina. In normal women, the presence of sufficient estrogen in the body, together with the lactobacillus bacteria in the vagina, keeps the vagina in an acidic environment, which effectively inhibits the reproduction of pathogenic bacteria and has a self-cleaning and sterilizing effect on the reproductive system. When inflammation occurs in the reproductive tract, a rise in pH can be detected and the environment in the vagina will change.