Kelly Osbourne says the "scariest things" she's ever experienced were her parents' medical emergencies.

The 39-year-old star will never forget the terror of seeing her mother Sharon need an emergency blood transfusion in 2002 when the former 'X Factor' star was being treated for colon cancer, or when her rocker dad Ozzy Osbourne was involved in a near-fatal ATV accident in 2003.

In an episode of 'The Osbournes Podcast' dedicated to their "biggest fears", the family began discussing the scariest things they have ever experienced.

Kelly told 71-year-old Sharon: "I know exactly what it was. I... had one with you, and I had one with Dad.

"It was watching you in the hospital when I kept telling them to take your blood pressure, and they wouldn't take your blood pressure, and they finally did, and they realized that you had to have a blood transfusion so quickly that they did it in the room.

"Seeing that was one of the scariest things I've ever seen in my life."

And recalling how Ozzy, 75, was involved in the accident when he and Kelly were in England promoting their duet 'Changes', she added: "It was just me and Dad that was the scariest thing ever."

The crash left the 'Paranoid' hitmaker with multiple injuries, including a broken collarbone and six broken ribs.

Meanwhile, Sharon and Kelly admitted Ozzy sometimes doesn't like their topics of discussion, so will walk out of recording.

Sharon told People magazine: “The other day we were doing a show and Ozzy didn't like the subject, so he put his shoes on and said, ‘I'm going, I don't like this.' "

Her daughter quipped: “If we see him putting his shoes on, we better change the subject real quick because he's going to get up and leave."

But the family know part of their appeal is their frank discussions.

Kelly said: “We can talk about absolutely anything and ask the questions that people want to know the answers to and do it in a way where you can push boundaries without insulting people. And if we do insult people on the way, sorry.”