Caroline Flack was rushed to hospital hours before the first 'X Factor' auditions began.
The 'Xtra Factor' host was taken ill at around midnight on Tuesday at her hotel in Liverpool and medics feared her symptoms - severe vomiting and a fever - were a result of a severe allergic reaction.
She was taken to a nearby hospital and treated before returning to her hotel - but then fell ill again, prompting show bosses to call a doctor.
A source told The Sun newspaper: "Caroline was delirious. She had no idea what was wrong with her.
"She feared she would have to miss the first show."
However, Caroline recovered in time to work on the first audition show, which saw Geri Halliwell join judges Gary Barlow, Tulisa Contostavlos and Louis Walsh on the panel.
Caroline tweeted: "After a VERY long night we are up and ready to roll! First auditions in Liverpool... and a new judge."
She later added: "Great day at auditions. Good work TEAM XTRA! No near death experiences next time yeh?"
Caroline is fronting 'The Xtra Factor' alone during the audition stages as co-host Olly Murs is touring the US with One Direction.
He will join her on the ITV2 spin-off show in time for the live stages of the contest.