The normal physiological vaginal discharge comprises vaginal secretions, exfoliated cells and cervical mucus. The frequency of vaginal discharge varies with age, menstrual cycle, pregnancy and use of oral contraceptives. The normal vaginal environment is characterized by a dynamic interrelationship between Lactobacillus acidophilus and other endogenous flora, estrogen, glycogen, vaginal pH and metabolic by-products of flora and pathogens. L. acidophilus produces hydrogen peroxide, which is toxic to pathogens and keeps the healthy vaginal pH between 3.8 and 4.2.
Vaginitis occurs because the vaginal flora has been altered by the introduction of pathogens or changes in the vaginal environment that allow pathogens to proliferate. Antibiotics, contraceptives, sexual intercourse, douching, stress and hormones can change the vaginal environment and allow pathogens to grow. Changes in the vaginal environment, such as an increase in glycogen production in pregnancy or altered estrogen and progesterone levels, enhance the adherence of C. albicans to vaginal epithelial cells and facilitate the germination of yeast. These changes may transform an asymptomatic colonization into a condition of symptomatic infection.