Rihanna's signature RiRi Woo lipstick at one of her gigs.
The New Yorker was at Rihanna's concert in Manhattan's Barclays Centre on 7 May. A Mac Cosmetics stall there was selling Rihanna's lipstick and the woman decided to sample it.
The lawsuit says that the staff member who applied the lippy "didn't use a fresh or new lipstick tube, but rather one that had been used for other patrons," they just told her to "press her lips together and spread the lipstick around".
A couple of days later the woman found a cold sore on her lip which was diagnosed by a doctor as oral herpes.
The lawsuit says that "Mac 'should have known' they were 'exposing patrons to possible spread of disease'" and the 28-year-old waitress told the New York Daily News that "This is going to happen over and over again if nothing is done,"
Then added: "I wasn't able to work for two weeks. It cost me a lot of money."4music
The case is still being heard, however lawyers have asked that Mac use "disposable lipstick or sanitised swabs" and "improve hygiene training" for staff at future Rihanna concerts.
Rihanna is due to hit stages in the UK on 10 June. Will you be testing her lipstick?