A model has filed a complaint against the car maker Hyundai, claiming she was fired from a job for having her period.
Rachel Rickert, 27, says she was "shamed" while representing the brand at the New York International Auto Show in April.
She says she made clear that she needed a toilet break, but was told it was too busy a time. She did not make it in time to change her tampon.
Hyundai Motor America says it is investigating the allegations.
Ms Rickert says she needed to change her underwear and tights, and told her talent rep Erika Seifred what had happened.
She later got a text from Ms Seifred saying the client - Hyundai - wanted her to take the night off.
The model told the BBC that she resisted, saying she would rather stay as she was being paid by the hour.
She went to work the next day, 14 April, as normal.
Ms Rickert says the rep then called on 15 April, saying that Hyundai no longer wanted her to work at the show because they heard about her period.
"I was completely puzzled," she told the BBC. "I was really upset. I started crying... I book out shows, and I miss other opportunities. So I was just like - 'What? This is not right!'"
'It's a natural thing'
The model has made a discrimination complaint to the US Equal Employment Opportunity Commission (EEOC) against Hyundai and Ms Seifred's management firm, Experiential Talent.
Ms Seifred told the BBC she did not wish to comment.
The model, who has taken part in 50 similar conventions, said she felt "shamed" by the brand's alleged behaviour.
"I'm not going to let people treat women this way," she told the BBC. "It's a natural thing that we have, our periods, and it's not like I want special treatment because of it. I just want to be respected as a human and to be able to go to the restroom. And not to be considered a bad employee because I needed to use the bathroom."
Hyundai Motor America told the BBC it has not yet received an EEOC filing, but is looking into what happened.
A spokesperson said: "We take any complaint like this seriously and will respond appropriately once we have a chance to investigate the merits of the claim."