Darlington threw away a two-goal lead and had to settle for a share of the spoils after a lively encounter in which the home side ended the game with only nine men.
The home side desperately need every point that they can get if the are to haul themselves away from the foot of the table, and after going 2-0 up against play-off chasing United the three points were almost in the bag for the second bottom club.
Under new manager David Hodgson Darlo had failed to score but in this game they looked dangerous from the start and the travelling Iron were kept on the back foot.
Tom Evans was the busier of the two keepers as Darlington went close through Barry Conlon and Neil Wainwright in the opening ten minutes of the game.
Evans was called into action to keep out a curled free kick from Craig James in the 19th minute, and was called repeatedly called into action again to keep his side in the game. The home side dominated and the Scunthorpe frustraion began to boil over, with centre-back Cliff Byrne booked for a foul on Conlon.
Home defender Ryan Valentine fired straight at Evans in the 34th minute but Evans was finally beaten four minutes later when Conlon broke clear before firing under the United keeper to open the scoring.
In the second half the visitors had the first opportunity to equalise through on-loan striker Steven MaClean, he steered a Peter Beagrie cross narrowly wide in the 55th minute.
Darlington doubled their advantage three minutes later when Wainwright volleyed in from 15 yards after an Ashley Nichols cross was only half cleared.
The second goal looked to be enough to seal a home win, but the game turned on its head in the 67th minute.
United defender Andrew Butler went down after appearing to be punched by Valentine, referee Tony Leake showed a straight red card to the midfielder and United scored through substitute Steve Torpey from the following free-kick. Suddenly it was Darlington's turn to panic.
Amazingly the home side were down to nine men ten minutes from time,w hen again Butler dramatically went down clutching his face - this time thanks to a headbutt from Barry Conlon.
Conlon became the second home player to be shown a straight red for violent conduct, and a penalty kick was awarded against the Darlington striker. Beagrie fired the textbook spot kick into the roof of the net to give his side the equaliser.
United continue to push for an unlikley win, but could have no complaints after getting a point out of the game thanks to the undiscipline of the Quakers.