Charni Ekangamene's first goal at this level, with the Reds' only noteworthy shot on target, opened the scoring but the home side responded quickly thanks to a Conor Henderson penalty.
A dreadful surface at Underhill did not help either side develop a passing game and the first half was littered with free-kicks. Bellerin was booked for a foul on Jesse Lingard early on and that set the tone for some strong challenges from both sides.
Pierluigi Gollini was equal to a Henderson free-kick but the Reds defended stoutly until Isaac Hayden was allowed a far-post header from a free-kick after he had been involved in a flare-up with Sean McGinty. Thankfully, the Gunners forward nodded wide.
A moment of magic by Ekangamene illuminated proceedings on 40 minutes as the Belgian midfielder rocketed a rasping drive past Emiliano Martinez after Larnell Cole latched onto a Marnick Vermijl pass down the line to pull the ball back to the edge of the area.
The lead was short-lived, however, as the impressive Bellerin was felled by Lingard inside the box and a rather soft penalty was awarded. Up stepped Henderson to hammer his spot-kick straight down the middle after Alexander Büttner, rather than Lingard, was shown a yellow card - presumably for dissent.
Despite the goals, things remained untidy after the interval and Lingard did receive a caution after a reckless tackle on Francis Coquelin, even if the Frenchman made a meal of it. Adnan Januzaj, working his socks off as a lone attacker with little reward, drifted a rare shot well wide