Were previous reality stars not allowed in CBB until recently?
 

It certainly applied for the civilian series as I remember reports about PJ and Tim from BB3 cheating to get in having appeared in The Villa on Sky 1 before. It's just that Sophie Anderton is likely to go in despite having already done I'm a Celebrity which Kerry Katona and Razor Ruddock had also been in years before entering the CBB house. Also not forgetting Rylan winning last series despite participating in the X Factor months before.

Yes, Producers of the C4 CBB definitely avoided anyone who had appeared on I'm A Celebrity, which I guess was the only other major reality show out there at the time.
Most of the US housemates from C4 CBB had appeared on reality shows in the US though.
Kerry Katona opened the flood gates when the show moved to Channel 5.

Kerry Katona was actually approached by Channel 4 bosses for their last Celebrity Big Brother in 2010, but she failed the psychiatric tests at the time.

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