The Toxic singer, 42, has told her Instagram followers the potentially deadly incident happened six months ago, and was the result of her security not lighting it for her.
She told her 42 million followers in a video clip, in which she spoke in a British accent: "I was in my room, I turned the fire on, and all of the sudden, it blew up in my face."
Spears added her fireplace had "done that before", and she usually gets her security to "come in and light it for" her.
View this post on Instagram A post shared by XILA MARIA RIVER RED (@britneyspears)
"But this time, I just threw the whole thing in there, and it literally blew into my face … it took all my eyelashes off, my eyebrows and – see these baby bangs? These are from … it sizzling all my hair."
Spears also told how she feared she had second or third-degree burns and thought she was going to have to "go to the emergency room" as her "face was, like, on fire".
"It hurt to touch my phone. It hurt to put ice on my face.
"It hurt to have anything touch it. This happened for, like, six or seven hours.
"The pain never went away. It was so, so, so bad."
Britney said she turned to taking paracetamol to go to sleep, adding: "Yeah, it was really bad."
But she concluded: "All is good now."
Britney opened up in 2023 about a fire she accidentally started with candles in her home gym, and showed off the burnt remnants after the accident on her Instagram.