A mum claims she was badly scalded by a "poorly put together" McDonald's cup of hot water.
Rosie Chapman from St Albans, Herts, posted pictures of brutal burns on her legs.
Snaps show blisters and sores on her inner thighs and her legs wrapped in medical plastic.
The 28-year-old says she may need a skin graft following the alleged incident on Friday October 16.
Rosie claims the accident took place at 10.40pm in a car park near the McDonald's in Hemel Hempstead.
She accused McDonald’s of “lacking compassion” and telling her to leave after the incident took place.
Posting to the McDonald's UK Facebook and on Twitter, Rosie claimed: "After a poorly put together cup containing scalding hot water, refused to be let into the store for a wet towel water ice everything I was screaming in pain for.
"After sitting on the floor in the bathroom with my skin blistering, I was crying scared in pain, being told to leave as it was closing time!
“I may possibly need a skin graft.
"Please explain why your staff are so poorly trained, your drinks could be hot enough to cause this and where the hell was any ounce of compassion for the pain and suffering, I was dealing with."
Rosie added: "The security guard on the door refused to let me in.
"The manager asked me to leave and to stop screaming once I finally got let in.
"The manager wouldn't give me any assistance. Not one tap in the bathroom had an option for cold running water.
"You will see from the CCTV exactly how it all panned out.
"I'm so upset with how little compassion any of the staff had that night. I was not some teenager loitering outside being a nuisance.
"I'm a mother to three children. Who I cannot care for at this moment in time."
Rosie’s tweet has shocked social media users.
A McDonald's spokesperson responded: “The health and safety of our people and our customers is our priority, and we are sorry to hear about this incident.
“Having investigated the incident with the restaurant, we understand the team offered assistance to the customer as soon as they were made aware of what had happened.
“Our Customer Services Team is currently in contact with the customer.”