Norway striker Carew goes into Tuesday night's clash with leaders Southampton on the back of three goals in his last three games.
Allardyce, whose side will leapfrog Saints with a victory at St Mary's, said: "When you are 6ft 5ins with that amount of ability and strength, he takes some stopping.
"He has a goal in his last three games, two for us and one for his country, and he is in a goal mood."
Allardyce played Sam Baldock alongside Carew against Blackpool on Saturday and the former MK Dons frontman hit his first two goals for the club in the resounding 4-0 win.
"That will give him a huge amount of confidence," added Allardyce.