Chelsea are not in a position to go into the market as things stand either because of FIFA's transfer ban, which they intend to appeal against.
Di Santo, 20, confirmed his progress with his first goal for Blackburn in the 3-2 derby victory against Burnley at Ewood Park.
David Dunn and Pascal Chimbonda were also on target while Robbie Blake and substitute Chris Eagles replied for the visitors.
On the possibility of Di Santo staying, Allardyce said: "I do not think that there is any real chance of that.
"There is a transfer ban on Chelsea and with the African Nations coming up they will probably need him.
"Di Santo was terrific - he is a young man learning his trade. He has finally got a chance to start some games and he has grasped it.
"What pleased me was the lay-off for Dunny's goal. He will take confidence as well from his first goal in the Premier League. If he can continue to play like this it will be good for us and Chelsea."
Burnley manager Owen Coyle complained to referee Chris Foy after the game about Di Santo's goal as he felt goalkeeper Brian Jensen had been obstructed.
Coyle said: "I was convinced that Di Santo had moved into Stephen Jordan and did enough to put Brian off. That was my initial thought and you won't convince me otherwise.
"Those marginal decisions are going against us. But referees do the job to the best of their ability and I am not going to get caught up in that. We just have to get on with it."
Blackburn's experience proved crucial with Dunn taking the man-of-the-match award after scoring his fifth goal of the season.
Playing just in the hole behind the striker the 29-year-old is in the form of his life, according to Allardyce.
He said: "Dunny is not only our leading scorer but he is providing others the opportunity to get goals. He is doing a terrific job.
"He can change games and put us back in contention against Burnley very early.
"That was important from our point of view. It wasn't an easy finish from him but he made it look easy."
It was Burnley's fifth straight defeat in the league on the road but Coyle added: "We will turn the corner, I am sure of that.
"We have scored two goals but got no points. However that away win is around the corner. We will continue to play on the front foot as that is what our fans deserve.
"It was a great start by us and a terrific goal from Robbie then we conceded some soft goals."
Chelsea 1/5, Draw 5/1, Blackburn 14/1