Bacterial vaginosis: how it differs from a yeast infection
Bacterial vaginosis (BV) is a disruption of the natural balance of bacteria in the vagina which, according to the NHS, shows up as a greyish-white, watery discharge with a strong fishy smell, but usually without itching or pain. A yeast infection (thrush, candidiasis) produces a white, cottage-cheese-like discharge with no smell, together with itching and burning. The two are treated differently – BV with an antibiotic, thrush with an antifungal – so if your symptoms are unclear, you need to be examined.
- According to the NHS, the typical sign of bacterial vaginosis is a strong fishy smell, especially after sex, with a greyish-white, thin and watery discharge.
- BV does not usually cause itching or pain, whereas thrush, according to the NHS, causes itching, irritation and burning during sex or when peeing.
- Around half of women with BV have no symptoms at all.
- BV is not considered a sexually transmitted infection, but sex can trigger it; the risk is higher after a change of partner, with an IUD and with perfumed products.
- BV often comes back within a few months, and if you have more than 4 episodes a year, a vaginal antibiotic gel may be prescribed for a longer period.
What are the symptoms of bacterial vaginosis?
According to the NHS, the most characteristic sign is an unusual vaginal discharge with a strong fishy smell, especially after sex. The discharge may become greyish-white, thin and watery. An important detail: BV does not usually cause itching or soreness, and around half of women with BV have no symptoms at all. If you are not sure what is causing the change in your discharge, the NHS recommends checking for other possible causes too.
How can I tell bacterial vaginosis from a yeast infection?
The two conditions are often confused, but according to the NHS they each have their own "signature":
- Discharge: with BV it is greyish-white, thin and watery; with a yeast infection (thrush) it is white, with a cottage-cheese texture.
- Smell: with BV – strong and fishy, especially after sex; with thrush the discharge usually has no smell.
- Itching and pain: BV does not usually cause itching or soreness; thrush causes itching and irritation around the vulva and vagina, as well as soreness and stinging during sex or when peeing.
- Cause: BV is a disrupted bacterial balance; thrush is an overgrowth of the Candida fungus, which normally lives in the body.
- Treatment: BV is treated with an antibiotic (tablets, gel or cream); thrush – with an antifungal (tablet, vaginal pessary or cream).
Neither one is classed by the NHS as a sexually transmitted infection. If this is your first episode or you are not sure, do not self-treat – an examination is the only way to find out which one it is and to rule out a sexually transmitted infection.
Why does bacterial vaginosis develop?
According to the NHS, BV is caused by a change in the natural balance of bacteria in the vagina, and the exact cause is not fully understood. You are more likely to develop it if you are sexually active (although it also occurs in women who have never had sex), after a recent change of partner, if you use an intrauterine device (IUD) and if you use perfumed products in or around the vagina.
BV is not a sexually transmitted infection, but sex can trigger it, and it can be passed on to a partner with a vagina. The NHS also notes that BV may increase the risk of catching a sexually transmitted infection, probably because it makes the vagina less acidic and weakens its natural defences.
How is BV diagnosed and treated?
According to the NHS, the diagnosis is made by a GP or a sexual health clinic, where you will be asked about your symptoms, your vagina may be examined and a sample of the discharge may be taken with a cotton swab to test for BV and other infections. Sexual health clinics often work without an appointment and give results more quickly.
Treatment is usually with an antibiotic – tablets, gel or cream. A partner with a vagina may also need treatment. The NHS warns that BV often comes back, usually within a few months, and then an antibiotic is prescribed again. If it recurs more than 4 times a year, an antibiotic gel to use in the vagina may be prescribed for several months, and your doctor can help you identify the triggers – for example sex or your period.
How can I reduce the risk of BV coming back?
The NHS advice is aimed at protecting the natural balance:
- wash your intimate area with water and plain soap, and prefer showers to baths;
- do not use perfumed soaps, bubble bath, shampoo or shower gel in the bath;
- do not use vaginal deodorants, vaginal douches or intimate "washes";
- do not put antiseptic liquids in the bath;
- do not wash your underwear with strong detergents;
- do not smoke.
When should you see a doctor?
According to the NHS, bacterial vaginosis is not usually serious, but it often needs an antibiotic, so contact a GP or a sexual health clinic if:
- you suspect you have BV – a discharge with a strong fishy smell, greyish-white and watery;
- you are pregnant and have symptoms – in this case the NHS advises getting treated promptly, because BV carries a small risk of complications such as premature birth or miscarriage, although in most pregnancies it does not cause problems;
- you notice a change in your discharge during pregnancy – talk to your doctor or midwife;
- your symptoms come back after treatment or recur more than 4 times a year;
- you are not sure whether it is BV, thrush or something else.
Frequently asked questions
Is bacterial vaginosis a sexually transmitted infection?
No. According to the NHS, BV is not classed as a sexually transmitted infection, although sex can trigger it and it can be passed on to a partner with a vagina.
Is bacterial vaginosis dangerous in pregnancy?
The NHS states that in most pregnancies BV does not cause problems, but it carries a small risk of complications such as premature birth or miscarriage, so if you have symptoms it is important to get treated promptly.
Can I treat BV with over-the-counter thrush medicines?
Not a good idea. According to the NHS, BV is treated with an antibiotic, and thrush – with an antifungal. If you are not sure which of the two you have, an examination with a swab of the discharge gives the answer.
Sources
- NHS – Bacterial vaginosis – last reviewed by the NHS: 19 June 2026
- NHS – Thrush in men and women – last reviewed by the NHS: 28 July 2023
Informational article retold in our own words from the sources listed. It does not replace a consultation with a doctor; in an emergency call 112. If you spot an inaccuracy, write to [email protected].