Dr Vanessa Mackay, spokesperson for the Royal College of Obstetricians and Gynaecologists, told The Sun that "it's a myth that toothpaste will tighten the vagina".

"Putting toothpaste into the vagina, or on the vulva, would not only be uncomfortable but it could also cause serious damage and disrupt the natural flora of the vagina, leading to the potential for infections like bacterial vaginosis and thrush," she said. 

Nigerian doctor Oluwole Yusuf issued a similar plea to women via the News Agency of Nigeria last week.

"Toothpaste is caustic and too abrasive for a sensitive body part like the vagina and using such on it can destroy the organisms meant to protect the vagina from possible infections," he said. 

He even warned that the dangerous practice might impact fertility. 

"When the vagina can no longer protect itself, the body is prone to infections which could later destroy the tubes and block the chances of getting pregnant.''

The trend follows a similar warning for men earlier this year after many started rubbing toothpaste on their penises, with the aim of increasing erections. 

A number of YouTube videos advised men to "massage toothpaste on the tip of your penis" in order to "crush premature ejaculation and erectile dysfunction".

But medical experts warned it could lead to burns, blisters and scarring.

It's not the first bizarre DIY method to be used on genitals. An old wive's tale resulted in a trend of women sticking garlic cloves up their vaginas to treat thrush a few years ago, and actress Gwyneth Paltrow famously encouraged vaginal steaming on her wellness website Goop.