Collison has been sidelined since May because of his troublesome knee problem, while Diarra has been restricted to just two appearances due to a thigh strain, but both are closing on full fitness.
The Hammers are in need of reinforcements as their squad is also without Mohamed Diame, Ricardo Vaz Te, Andy Carroll, and Yossi Benayoun, who are all sidelined through injury.
Diame is the most recent arrival in the treatment room as he suffered a hamstring problem in Sunday's 3-2 defeat by Liverpool.
Allardyce told the Daily Mirror: "Diarra is close, but he hasn't played a Premier League game yet.
"He hasn't felt what it is like to play there and that would be difficult after a three-month lay-off.
"Collison might be close to start joining in again over the next few weeks."