Usually, "good" bacteria (lactobacilli) outnumber "bad" bacteria (anaerobes) in your vagina. But if anaerobic bacteria become too numerous, they upset the natural balance of microorganisms in the vagina and lactobacilli decrease.
Factors that can disrupt the balance of bacteria in the vagina include:
- Reacting to antibiotics
- Using an intrauterine device (IUD)
- Having unprotected sex with one or more partners
- American College of Obstetricians and Gynecologists. (n.d.). FAQ: Vaginitis. Retrieved May 10, 2012, from http://www.acog.org/~/media/For%20Patients/faq028.pdf?dmc=1&ts=20120510T1238147389 (PDF - 285 KB)
- Centers for Disease Control and Prevention. (2010). Bacterial vaginosis: CDC fact sheet. Retrieved May 10, 2012, from http://www.cdc.gov/std/bv/STDFact-Bacterial-Vaginosis.htm
- Department of Health and Human Services, Office on Women's Health. (2008). Bacterial vaginosis fact sheet. Retrieved May 10, 2012, from http://womenshealth.gov/publications/our-publications/fact-sheet/bacterial-vaginosis.html