The best-of-seven series now move to Chicago and Dallas, respectively, with both third games to be played in two days.
There are three NBA playoff games scheduled for today, when both top seeds are in action. The Cleveland Cavaliers host Game 2 of their Eastern Conference series against Detroit, while the Los Angeles Lakers are home to Utah for the second game of their Western Conference series. The Portland Trail Blazers host the Houston Rockets in the third game.
In Boston, Allen scored 28 of his 30 points in the second half to help the Celtics avoid losing two straight games at home. Allen scored 16 points in the fourth quarter and hit two 3-pointers in the final minute, including the game-winner over the fingertips of Chicago's Joakim Noah.
Glen Davis, starting for Boston in place of Kevin Garnett, added 26 points and nine rebounds. Rajon Rondo finished with 19 points, 12 rebounds and 16 assists for the second-seeded Celtics, who had lost the opening game of the Eastern Conference series 105-103 in overtime.
Ben Gordon scored a game-high 42 points for the Bulls.
In San Antonio, the Spurs opened a 30-19 lead after one quarter against Dallas. Tim Duncan had 13 points, 11 rebounds and three blocks.