The Scottish striker's days in Lancashire appeared over when he spent most of last season with Plymouth.
But Allardyce insists Gallagher has a chance to stake a claim for a first-team place in pre-season following the departures of Roque Santa Cruz and Matt Derbyshire.
"It's down to Paul," the Blackburn boss told the club's website.
"He had one of the brightest futures of any young player here many years ago under Graeme Souness.
"If Paul wants to change his outlook on how he wants to develop his career, he is at a great place to do it.
"The talent is not in question, the desire to be a Premier League player is what Paul needs to have. If he can show that then we have a terrific player at Blackburn."