C&A was appointed last week without a pitch to handle an account which, it is understood, could be worth up to £150,000.
LF is lavishing £20m on the UK relaunch of the brand - which will return to stores in the middle of March - as it bids to revive the success it enjoyed in the 1960s and 1970s.
In the UK Sunsilk shampoos and conditioners were discontinued more than a decade ago. Sunsilk hairspray was discontinued at the end of last year.
During the past five years, the brand has been re-launched in various markets outside the UK.
C&A deputy MD Charlotte Clarke, who reports to Sunsilk senior brand manager Bella Skinner, said: 'Apart from its name, the brand bears no similarities with the old Sunsilk.'
C&A also handles consumer PR for LF's Impulse, Sure, Timotei, Vaseline Intensive Care and Persil Non-Bio brands.