Bacterial vaginosis: causes, treatment and why it keeps coming back
In 30 seconds
Bacterial vaginosis (BV) is a common cause of unusual vaginal discharge1. Across the world, around a quarter of women of reproductive age have it at any one time3. It is usually not serious, but it can be frustrating because it often comes back.
What happens in BV
A healthy vagina is usually dominated by lactobacilli, “good” bacteria that keep it slightly acidic. In BV, these bacteria drop and other bacteria overgrow4. The vagina becomes less acidic, which lowers its natural defences1.
Doctors don’t fully know why this happens. But BV is more likely if you1:
- are sexually active (though people who have never had sex can get it too)
- have a new partner
- have an IUD (copper coil)
- use perfumed products in or around the vagina
Symptoms of BV
- unusual discharge with a strong fishy smell, especially after sex1
- discharge that becomes grey-white, thin and watery1
BV does not usually cause itching or soreness. Half of women with BV have no symptoms at all1.
| Question | Answer |
|---|---|
| Is it an STI? | No, but sex can trigger it or pass it on between women |
| Main sign | Thin grey-white discharge with a fishy smell |
| Itching? | Not usually |
| Treatment | Antibiotic tablets, gel or cream |
| Comes back? | Often, usually within a few months |
| Partner treatment | Women partners may need treatment too |
How BV is treated
BV is usually treated with antibiotic tablets, or a gel or cream put into the vagina, prescribed by a GP or sexual health clinic1. If your partner is a woman or has a vagina, they may also need treatment1.
Why BV keeps coming back
It’s common for BV to return, usually within a few months1. In one study of women treated with oral antibiotics, 58% had BV again within a year2. If you get BV more than 4 times a year, you may be offered an antibiotic gel to use for a few months to help stop it returning1.
Why treating BV matters
BV raises the chance of getting an STI, possibly because the vagina is less acidic1. A meta-analysis found BV was linked with about a 60% higher risk of getting HIV7. In pregnancy there is a small chance of complications such as premature birth or miscarriage, although most pregnancies are not affected1.
When to see a doctor
- You think you have BV, especially if it’s the first time1.
- You’re pregnant and your discharge changes1.
- BV keeps coming back. You’ll usually be offered tests for STIs and HIV too5.
- You have bleeding after sex or between periods.
- Pain in your lower tummy or pelvis with a fever, unusual discharge or bleeding could be PID. Ask for an urgent GP appointment or call 111. Call 999 or go to A&E if the pain is severe, you have a very high temperature, feel faint, or could be pregnant8.
Quick check: Does BV usually cause itching?
No. BV mainly causes a thin, fishy-smelling discharge. Itching is more typical of thrush1.
References
- NHS. Bacterial vaginosis. www.nhs.uk/conditions/bacterial-vaginosis/
- Bradshaw CS, Morton AN, Hocking J, et al. High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy and factors associated with recurrence. J Infect Dis. 2006;193(11):1478-1486. doi.org/10.1086/503780
- Peebles K, Velloza J, Balkus JE, McClelland RS, Barnabas RV. High global burden and costs of bacterial vaginosis: a systematic review and meta-analysis. Sex Transm Dis. 2019;46(5):304-311. doi.org/10.1097/OLQ.0000000000000972
- Ravel J, Gajer P, Abdo Z, et al. Vaginal microbiome of reproductive-age women. Proc Natl Acad Sci USA. 2011;108(Suppl 1):4680-4687. doi.org/10.1073/pnas.1002611107
- Workowski KA, Bachmann LH, Chan PA, et al. Sexually Transmitted Infections Treatment Guidelines, 2021: Bacterial vaginosis. Centers for Disease Control and Prevention. www.cdc.gov/std/treatment-guidelines/bv.htm
- Senok AC, Verstraelen H, Temmerman M, Botta GA. Probiotics for the treatment of bacterial vaginosis. Cochrane Database Syst Rev. 2009;(4):CD006289. doi.org/10.1002/14651858.CD006289.pub2
- Atashili J, Poole C, Ndumbe PM, Adimora AA, Smith JS. Bacterial vaginosis and HIV acquisition: a meta-analysis of published studies. AIDS. 2008;22(12):1493-1501. doi.org/10.1097/QAD.0b013e3283021a37
- NHS. Pelvic inflammatory disease. www.nhs.uk/conditions/pelvic-inflammatory-disease-pid/
How we rate evidence. Strong: systematic reviews, large studies or national and international guidelines. Moderate: a single good-quality study, expert reviews or official guidance on a narrower question. Limited: one observational study or little direct research. Early: small or pilot studies that need confirming.
This article is for general information and does not replace medical advice. If you are worried about your symptoms, contact your GP, a sexual health clinic, NHS 111 or, in pregnancy, your midwife.
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