Oral sex linked to vaginal condition that causes 'strong fishy smell'

Scientists have discovered a link between oral sex and bacterial vaginosis (BV) - a vaginal condition that causes a strong fishy smell.

The team from the University of California, San Diego, suggest that bacteria introduced during oral sex could increase the risk of BV.

BV is a common cause of unusual vaginal discharge, and while it is not a sexually transmitted infection, it can increase your risk of getting an STI such as chlamydia.

The NHS explained: “The most common symptom of bacterial vaginosis is unusual vaginal discharge that has a strong fishy smell, particularly after sex.

“You may notice a change to the colour and consistency of your discharge, such as becoming greyish-white and thin and watery.”

While BV is very common, until now, the mechanism behind the condition has remained unclear.

In the new study, the researchers conducted experiments in both mice and human vaginal specimens.

Firstly, the mice were treated with Fusobacterium nuleatum - a bacterium found in the mouth and linked with gum disease.

The results revealed that this exposure increased biochemical activities linked with BV.

Next, human vaginal specimens from 21 women were exposed to the bacterium, and again, the results showed that this increased their risk of BV.

In a statement about the findings, the researchers, led by Kavita Agarwal, explained: “The experiments led to the discovery that Fusobacterium nucleatum does not act in a simple one-way relationship with other bacteria, but may engage in a mutually beneficial relationship, potentially encouraging dysbiosis (microbial imbalance) in susceptible vaginal communities.

“Fusobacterium was helped by bacteria in BV-like communities that produce an enzyme called sialidase, enabling Fusobacterium to consume sialic acids from mucus produced by the host.

“Fusobacterium also acted by unknown mechanisms to greatly benefit the growth of Gardnerella vaginalis, a sialidase producer believed to be a key player in BV.”

In humans, fusobacterium can be found in our mouths, and overgrows in dental plaques.

The researchers added: “Fusobacterium is widespread in human mouths and overgrows in dental plaque; the authors speculate that it may be introduced during oral sex, which has been identified in some clinical studies as a risk factor for BV.”

If you suspect you have BV, the NHS recommends visiting your GP or sexual health clinic.

It explained: "Bacterial vaginosis is usually treated with antibiotic tablets or gels or creams. These are prescribed by a GP or sexual health clinic."