The Toffees were reduced to 10 men when the Wales international caught Ashley Barnes with a raised elbow, and his coach was quick to dub the challenge "unprofessional".
"Ashley Williams getting sent off sums our day up. It shouldn't happen, he's swung his arm and he's an experienced player," Allardyce told BBC Sport.
"No complaints with the red card, you can't do that. It was unprofessional."
Everton's fifth away defeat on the bounce leaves them in 10th place in the table.