Sebastian Larsson put the home side in front after 12 minutes at the Stadium of Light, with Adam Johnson and James McClean firing second-half goals to cap off a forgettable day for the Hammers.
Allardyce was particularly unhappy with the defending that led to Sunderland's second goal, where a comedy of errors allowed Johnson to score.
He said: "Just look at it, it was pathetic, wasn't it? We have a free-kick and we let the opposition score.
"Jussi (Jaaskelainen) gets us out of jail in the first place by making a really, really good save, and then we mess up the clearance and they score, so it probably sums us up today.
"We didn't defend correctly, we didn't have the appetite for defending correctly and nullifying the opposition's strengths, we never passed the ball as well as we know we can.
"It was really an all-round performance that makes life extremely difficult for me to accept, the performance I have seen based on how well we played just seven days ago against Manchester United.
"The level of difference in performance between that game and this is just staggering."
Allardyce admits he will launch a recruitment drive for defenders after James Collins limped off with a hamstring tear, joining George McCartney and Joey O'Brien on the sidelines.
"The big blow for me is not having enough defenders at the moment. There are too many of my defenders injured," he said.
"We have had too many injuries recently, but the injury situation with defenders with George McCartney not being here, Joey O'Brien not being here and James Collins getting injured today means that the defensive side of our team is particularly weak and short of numbers now.
"I am really going to have to go and try to strengthen that area in the next few days."