Menstrual cups are more likely to cause rare toxic shock syndrome than tampons and should be sterilised between use, new research shows.

The study, published in Applied and Environmental Microbiology, tested eleven types of tampons and four menstrual cups to determine their effect on the growth of bacteria staphylococcus aureus, which produces toxic shock syndrome.

Menstrual toxic shock syndrome is a rare but severe disease, it said.

The study found a slight increase in the bacteria and toxin in menstrual cups because there was more air captured in vitro than that of tampons.

It also found the bacteria could stay and grow on the cup even after it was washed, and recommended switching between two and using boiling water to wash them.

Microbiologist Siouxsie Wiles said the finding was a worry.

“The advice is you just need to wash [menstrual cups] with water, actually what you need to do is sterilise them.”

She said sterilising the cups was the take-home advice for women looking to use them.

“Don’t use them for as long, and make sure you have several so you can make sure they’re properly sterilised and you aren’t putting bacteria back in.”

“They grow a huge amount and are producing what looks like a lot of toxin so that’s really scary.”