Bacterial vaginosis (BV) occurs when the balance of bacteria inside the vagina is disrupted, similar to how a yeast infection is caused by a fungal imbalance. In most cases, BV does not cause any pain or itching. The most common symptom is an unusual vaginal discharge.

The vagina is naturally a slightly acidic environment. This is due to a bacteria called lactobacilli. Lactobacilli produces lactic acid and the resulting acidity prevents vaginal bacteria from growing and reproducing. Women presenting with bacterial vaginosis tend to lack sufficient numbers of lactobacilli, which means the vagina isn’t acidic enough to prevent other bacteria from growing. It’s this imbalance of bacteria that causes BV.

It is not clear what exactly causes the imbalance that results in bacterial vaginosis, although certain factors are known to increase the chances of developing BV. These include:

• Being sexually active, especially if you have a new sexual partner or multiple sexual partners
• Using an intrauterine device such as a contraceptive that fits inside the womb
• Using scented soaps, bubble baths, or antiseptic bath liquids
• Using vaginal deodorants
• Using a strong detergent to wash your underwear

Bacterial vaginosis may sometimes be grouped in with sexually transmitted diseases such as chlamydia or herpes, but this is inaccurate — even women who aren’t sexually active can develop bacterial vaginosis, and it cannot be passed on. Also, the rates of BV are significantly varied within different ethnic groups, which cannot be explained by sexual activity alone.

However, it is apparent that BV symptoms are reported more frequently by women who have intercourse regularly with multiple sexual partners. In contrast, the rates of BV are lower in women who practice safe sex with fewer sexual partners. Clearly, sexual activity has a role to play in developing bacterial vaginosis, although several other unrelated factors are also likely to be responsible. In any case, it’s always best to practice safe sex to avoid contracting bacterial vaginosis (BV) or any sexually transmitted infections.

A sufferer of bacterial vaginosis is likely to experience the following symptoms.

Vaginal discharge that:

• Has a strong fishy odour that is particularly strong after sexual intercourse
• Is white or grey in colour
• Is thin and watery

Other (rarer) symptoms of bacterial vaginosis may include:

• Vaginal itching
• Burning during urination

Bacterial vaginosis does not pose a serious threat to health for the majority of sufferers. In fact, around half of those affected with BV don’t present any symptoms at all. BV should only be treated as a concern should the condition develop during pregnancy and there is a history of pregnancy-related complications.

Though commonly confused, BV and yeast infections are two entirely different conditions. In a yeast infection (usually referred to as thrush), vaginal discharge will have the consistency of cottage cheese, and present no odour.

Your first case of BV should always be diagnosed by your doctor or a healthcare professional. They will be able to rule out other causes of the symptoms such as thrush, chlamydia or gonorrhoea and ensure you get the correct treatment. Once your first case of BV has been diagnosed, subsequent episodes can be self-diagnosed as long as the symptoms are exactly the same as the previously diagnosed case. Repeated BV infections should be examined by your doctor to treat any underlying cause.

A GP or healthcare professional will be able to diagnose bacterial vaginosis from a description of the symptoms coupled with a visual examination of the vagina, if necessary. In the examination they will be looking for a thin, greyish discharge as well as an unpleasant smell. In most cases this will be enough to confirm a diagnosis. However, further testing may be necessary if you are sexually active. This is because the symptoms of BV can resemble the symptoms of some sexually transmitted infections (STIs), such as gonorrhoea and trichomoniasis. Further testing will usually involve a sample of cells being taken from the vaginal wall. This will be done using a plastic loop or swab. This sample is then examined in a laboratory to look for signs of bacterial vaginosis.

Another method of diagnosing BV may include performing a pH (acidity) test of the vagina. A swab will be used to take a sample from inside the vagina. This sample will then be wiped over a piece of specially treated paper. The paper will change colour depending on the pH level of the sample. If the paper indicates a pH higher than 4.5 then this will be a strong indication that bacterial vaginosis is the cause.