Bacterial vaginosis (BV) is a common vaginal infection that happens when the normal balance of bacteria in the vagina changes. It is not a sexually transmitted infection, but sex can make it more likely.
Bacterial vaginosis develops when some types of bacteria in the vagina grow more than usual and upset the natural balance. Doctors do not fully know why this happens. Things that can make it more likely include a new sexual partner, having several partners, using perfumed products or douching, and having an IUD. Some people get BV without any clear trigger.
The main sign of BV is unusual vaginal discharge with a strong fishy smell, often stronger after sex. The discharge may become thin, watery and grey or white. About half of people with BV have no symptoms at all. BV does not usually cause itching or soreness, which can help tell it apart from a yeast infection.
A GP or sexual health clinic can check for BV and prescribe treatment, usually antibiotic tablets, gel or cream. BV often comes back, so some people need treatment more than once. Avoiding perfumed soaps and washing the outside of the vagina with plain water may help some people.
Bacterial vaginosis in pregnancy can sometimes be linked to complications, so anyone pregnant who notices symptoms should speak to a midwife or doctor. BV is one of the most common causes of vaginitis.
Sources: NHS.