Dunn shines on attritional day
Watch highlights of day two
Zafar Ansari will find out tomorrow morning whether he can return to action in Surrey's LV= County Championship Division Two clash with Essex at the Kia Oval after receiving hospital treatment for concussion.
England batsman Ravi Bopara proved Essex's sole bastion of resistance, grinding out the top score of 49 as the visitors toiled to 225 for six at the end of the second day.
Spinner Ansari was discharged from hospital for further assessment by Surrey's medical staff after sliding head-first into the boundary fence today.
The 22-year-old hared onto Alastair Cook's back-foot off-drive after failing to collect at the first attempt and, in his desperation to atone, he slid straight over the boundary rope and into the fence.
The former England Under-19 slow bowler was back at The Oval by mid-afternoon, but did not return to the field of play on the second day of four.
Ansari will require the all-clear from Surrey's medics before he can return to action, with bowling coach Stuart Barnes praising his commitment, if not his judgement in chasing a lost cause.
"He's back; he was concussed, so he's in the hands of the medical team," said Barnes.
"The fielding coach Chris Taylor is pretty pleased with his desire to stop the ball; we're all thinking he's a bit of an idiot for doing what he did, but he's okay.
"I'm not sure what part if any he's going to play in this game, but he was back upstairs earlier on.
"I don't know what medically they prescribe when someone's had concussion, and I don't know how bad it was, so we'll just have to wait on that."
After Surrey won the toss following yesterday's washout, England captain Cook made 39 before Matt Dunn had him caught behind top-edging an attempted pull.
Rain forced an early lunch, with Essex 73 for one from 22.2 overs and Jaik Mickleburgh 30 not out.
Surrey were able to capitalise on the rain break to put Essex out of their rhythm, Mickleburgh unable to settle after play resumed at 2.15pm.
The Essex opener's uneasy toil came to an end when he edged Jade Dernbach to Surrey skipper Graeme Smith at first slip, for 38 from 114 balls.
Jason Roy had to fill in for Surrey in the absence of Ansari's spin, but it was Dunn who shouldered the greater responsibility.
The 21-year-old's two wickets in three balls handed the hosts hope of turning a meandering affair into a credible contest.
England Under-19 cap Dunn trapped Tom Westley for 31, just when the Essex number three would have been contemplating anchoring his side's static innings.
Greg Smith could only last two balls, nicking to Gary Wilson at second slip as Dunn picked up Surrey's pace.
Bopara, mindful of potential capitulation, kept his counsel until the tea interval, intent on producing little more than stabilising the innings by retaining his wicket.
Ben Foakes was unable to accelerate the scoring at the other end either, leaving Essex 159 for four at tea, from 52 overs.
Foakes hacked Stuart Meaker away for a one-bounce four after the break in a bid to kickstart proceedings, but Surrey's South Africa-born paceman quickly had the last laugh.
He skittled Foakes for 22 after a 54-ball stint that included three fours.
Bopara struck a four off Dernbach to edge Essex past 200, then delivered another boundary off the next ball and the same bowler.
Just when his fifty came squarely into view, Roy popped up to have him caught behind down the leg side one shy of the milestone.
Bad light eventually forced the teams from the field after 77.5 overs, with James Foster 19 not out from 48 balls and Graham Napier having mustered four from 20 balls.