Kalou spent six years at Chelsea before making the move last summer to France, where he enjoyed a productive debut campaign.
The 27-year-old has previously admitted that he misses Premier League football and has been linked with a number of English clubs, including West Bromwich Albion.
West Ham are also keeping tabs on Kalou and Allardyce believes it would be a good deal for the club, but he is not sure whether it will happen.
"As far as I know, back at West Ham, I think the chairman is speaking with the player's agent," Allardyce told Sky Sports News.
"We understand the player wants to come back and play in England, whether that is with us or with whoever, we are having a look at it.
"Obviously from his record at Chelsea, and his goalscoring record this season in France, and his age, he is very appealing to us.
"But whether that will come off or not in terms or what regular position he wants to play, may be the stumbling block."