Allen got three hits for the second straight day but the Athletics failed to hold a lead and fell to the Baltimore Orioles 6-2 on Monday night, their fourth straight loss.
David DeJesus doubled home a run and scored on Cliff Pennington's single for the A's, who have dropped four straight.
"It's part of the game," Allen said. "We got some good at-bats but their pitcher seemed to bear down when he felt a threat. Unfortunately they got the key hits and we didn't."
The Orioles managed only two hits off Oakland left-hander Gio Gonzalez (9-11) through the first six innings before scoring four times in the seventh.
"It was a positive outing," said Gonzalez, who lost his fifth straight start. "I took a stride forward. My luck is turning a little bit and I just want to stay positive."
Adam Jones and Vladimir Guerrero both singled before Gonzalez walked Wieters to load the bases. After a strikeout, Andino greeted reliever Fautino De Los Santos with a deep double over the head of center fielder Coco Crisp to drive in Jones and Guerrero.
Bell, batting only .143 coming into the game, followed with a bouncing single up the middle. Wieters and Andino both scored easily to make it 5-2.
"The seventh inning was a problem," A's manager Bob Melvin. "Based on how he pitched leading up to that it looks like Gio is righting the ship."
It's only Baltimore's fourth win in its last 18 games on the road. The Orioles also won for just the second time in 14 games at the Oakland Coliseum since the start of the 2008 season.
Tommy Hunter (2-2) allowed two runs over 6 2-3 innings to earn his first win with Baltimore. The right-hander, who struck out three and walked one, had been winless in two starts since being acquired in a trade from Texas on July 30.
He also got help from the Orioles defense, which turned a double play in the second inning. Wieters also threw out Jemile Weeks trying to steal, the 28th runner the Baltimore catcher has caught this season.
Hunter allowed 10 hits and improved to 5-0 in six career starts against the A's.
Oakland, outscored 23-8 while getting swept in a three-game series by Texas over the weekend, lost for the sixth time in seven games and fell a season-low 15 games under .500.
Gonzalez gave up four runs and four hits while walking three to raise his majors-leading total to 72.
The A's strung together four consecutive hits in the bottom of the inning to go in front.
Josh Willingham singled and scored on DeJesus' double to left center. Allen followed with a base hit before Cliff Pennington's RBI single gave Oakland a 2-1 lead.
It stayed that way until Baltimore scored four times in the seventh.
Reynolds, who had been in a 1 for 28 slump with 14 strikeouts, homered off Trystan Magnuson in the ninth.
Notes: The A's set an Oakland record with their 92nd consecutive game with two home runs or fewer. ... A's manager Bob Melvin expects Conor Jackson to be out a few days after the first baseman woke up with a sore neck. ... Baltimore IF Chris Davis was not in the starting lineup in order to rest a sore shoulder. ... Baltimore 3B Josh Bell underwent a CAT scan on his left side which proved negative. ... LHP Brian Matusz (1-4) is expected to be recalled from Triple-A Norfolk to start for Baltimore on Tuesday night. Matusz had a 0.56 ERA in his last two starts in the minors. RHP Guillermo Moscoso (5-6) will go for the Athletics.