The This Morning presenter recalled how she was injured during a particularly violent cake throwing incident on Ministry of Mayhem.
Former co-host Stephen Mulhern said: "We had Santa Claus one year and all he had to do was put a cake in Holly's face - simple.
"For whatever reason he picked up the one that was like a brick. He caked Holly and nearly broke her nose."
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Willoughby added: "I thought I was going to have a nosebleed but luckily I was all right."
Ministry of Mayhem featured a regular segment in which Willoughby would be heavily gunged or cream caked by crewmates and audience members.
She said: "For two years I smelled of cake - that cream smell lingered in my hair."
The pair made the comments on the upcoming programme 30 Years Of CITV, which will be brodcast on Saturday at 6.30pm on ITV1.
Watch Holly Willoughby getting gunged below: