National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention
Division of Sexually Transmitted Diseases
Program and Training Branch
The vagina is a dynamic ecosystem that normally contains approximately 109 bacterial colony-forming units per gram of vaginal fluid. The normal vaginal discharge is clear to white, odorless, and of high viscosity. The normal bacterial flora is dominated by lactobacilli, but a variety of other organisms, including some potential pathogens, are also present at lower levels.
Lactobacilli convert glycogen to lactic acid. Lactic acid helps to
maintain a normal acidic vaginal pH of 3.8 to 4.2. Some lactobacilli produce H2O2 (hydrogen peroxide), which kills bacteria and viruses.
Vaginitis is usually characterized by a vaginal discharge, vulvar itching and irritation, and a vaginal odor. The three most common diseases diagnosed among women with these symptoms include bacterial vaginosis
(40%-45%), vulvovaginal candidiasis (20%-25%), and trichomoniasis
(15%-20%). In some cases, the etiology may be mixed, and there may be more than one disease present.
Other causes of vaginal discharge or irritation include the following:
Normal physiologic variation
Allergic reactions, e.g., spermicides, deodorants
Herpes Simplex Virus (HSV)
Mucopurulent cervicitis--may be related to Chlamydia trachomatis or
Neisseria gonorrhoeae infection
Atrophic vaginitis--found in lactating and post-menopausal women and related to a lack of estrogen
Vulvar vestibulitis, lichen simplex chronicus, and lichen sclerosis (especially pruritis)