The Belgium international has been in impressive form for Villa, hitting 16 goals in 28 appearances since joining from Genk in the summer.
Allardyce has identified the 22-year-old as "the biggest threat" to his side as they look to take all three points off Paul Lambert's struggling side.
"[Benteke's] the biggest threat. He's the man who scores the goals for Aston Villa on a regular basis, he's the focal point for their attacks in that he not only scores goals, but he holds the ball up, he's strong," said Allardyce.
"He's had a fantastic start in what must have been a very disappointing season so far for Aston Villa. It says a lot for what he is as a player when he's producing what he is in a team that's been struggling for results.
"We can ill afford to let Aston Villa get off to the sort of start they did against Everton. We've got to avoid that at all costs and play our way into the game, making sure we don't give them any opportunities to score."
The Hammers currently sit in 11th place in the Premier League table.