However, Allardyce was disappointed that Dembele was not sent off when the scores were level.
"Consider the consistent bookings that Howard (Webb) gave our players," Allardyce told Sky Sports News. "But, after getting booked, Dembele fouled (Mohamed) Diame and the ref let it go.
"And, in the second half, he (Dembele) pulls Joe Cole back and then kicks the ball away. If he does that, he's got to send him off, that's what we're told, so I'm really disappointed.
"At 1-1, that makes a huge difference. I'll put it in my report and see if the boys agree with me. If they don't, I'd like to know why not."
West Ham face Stoke City on Saturday.