Jordan Rhodes fired Rovers ahead from the penalty spot on the stroke of half-time and only a magnificent late Tomasz Kuszczak save prevented the in-form Scotland international striker from adding to his tally. It would prove a vital intervention in the Championship tussle.
In the last of five additional minutes, Blackburn substitute David Goodwillie untidily sent Lopez tumbling in the box, leaving referee Robert Madley with little option but to award a spot-kick.
Lopez picked himself up to coolly convert and move Brighton to within four points of the play-off places in seventh.
Having lost Appleton's first game at the helm, Blackburn are five points further back in 14th.
The Rovers boss made two changes in midfield as Simon Vukcevic and Ruben Rochina made way for Pedersen and Markus Olsson, while Brighton playmaker Vicente was handed his first league start of the season by Gus Poyet at the expense of Craig Mackail-Smith. Gary Dicker replaced Dean Hammond in the visitors' midfield.
Brighton dominated possession during the opening stages and Ashley Barnes might have put them ahead in the 10th minute, failing to connect with Lopez's corner having found space.
But life on the counter-attack suited Rovers and Kuszczak was forced to keep Lowe's prodded effort out of the bottom corner following a driving run from Kazim-Richards.
Blackburn appeared to grow into the contest and the pressure told as the half came to a close when El-Abd bundled Pedersen to the ground from Martin Olsson's left-wing delivery.
Referee Madley remained unmoved but his assistant was well placed to flag for a penalty that Rhodes duly dispatched, sending Kuszczak the wrong way for his fifth goal in as many league matches.
Having watched his team resume proceedings on the back foot, Poyet decided to act nine minutes into the second half by sending on Will Buckley and Mackail-Smith in place of Vicente and Andrea Orlandi.
Goalmouth action had become virtually non-existent by the time Kazim-Richards turned to curl a low 25-yard drive past Kuszczak but into the side-netting.
Kuszczak then had to push another Kazim-Richards over the bar, but the former Manchester United goalkeeper saved his best work for the 84th minute when he somehow clawed Rhodes' looping header out of the far corner.
Lopez headed onto the roof of an unguarded net when Kean punched uncertainly at the start of injury time but he would soon be the hero.