Kelly Osbourne was filming her television show Fashion Police in front of a full studio audience when she turned to Melissa Rivers - daughter of comedian Joan - and said "I don't feel good", according to celebrity website TMZ.
The daughter of Sharon and Ozzy then reportedly fell out of her chair before the seizure begun.
An audience member, believed to be an emergency responder, ran up to help Ms Osbourne.
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One London Marathon runner who helped an exhausted competitor said it was "worth it" to help his rival.
The Irish Coast Guard helicopter went down into the Atlantic last month.
Thicker cloud across Ireland and northern Scotland but otherwise a very pleasant afternoon.