Student Brittany Forster, 24, was seen hyperventilating the moment she saw her lips, having used the small apple-shaped tool for two minutes.
The Australian told the Daily Mail: "I took it off and I just looked in the mirror and I said oh my god what have I done? No, no, no, this can’t be happening.
"As soon as I looked in the mirror I thought 'what have I done to myself?'.
"I was thinking it was permanent. When I put the lipstick on, I was like, well if this is my life now I'm going to have to start enjoying it. I’ll have to embrace it."
The CandyLipz device is available online, latching onto the user's lips and squeezing them to produce a plumper pout.
A spokesperson for the company said: "My, she got huge lips, we love it.
"It is very normal to get the cupping marks. These marks are temporary and will resolve within 7 days or less."
Four days after using the applicator, Brittany was left with a bruised mouth.
"They're still really blue and bruised, I look dead," she said.
"The next day they were still really red and quite big but now they’re just bloodied and bruised. I’m very appreciative of my little lips now. Grateful for what I have."