The visitors were on terms within 60 seconds of the restart, midfielder Lansbury rising to level with a superb header from 8 yards following a corner from Majewski.
Keeper Darlow prevented** **Brighton from regaining the lead only 3 minutes later by pushing a goal-bound shot from Barnes onto the post.
Two goals in the space of two minutes put Forest firmly in charge with a strike from Henderson and a spot kick by Lansbury boosting the visitors.
Forest were reduced to 10 men on 67 minutes when Chalobah, booked earlier for a foul, received a second yellow for a push on LuaLua.
LuaLua had a curling free kick saved by Darlow as the Seagulls struggled to launch a late fightback.
LuaLua forced keeper Karl Darlow to make a scrambling save in only the third minute after being fed by Stephen Ward, and two minutes later he fired an angled shot over the bar from inside the area.
Darlow later dived to hold a bouncing 30 yard drive from Ashley Barnes before Forest came close to breaking the deadlock.
An accurate cross from Andy Reid found striker Henderson and his goal-bound header was pushed round the post by Polish goalkeeper Tomasz Kuszczak diving to this left.
Kuszczak was alert again mid-way through the first half when he beat away a firm drive from fellow countryman Radoslaw Majewski.
Lansbury and Reid both put shots wide for Forest before Wales international Crofts put Brighton ahead in the 31st minute from close in.
Lansbury levelled the scores just after half-time, with Forest going in at the interval trailing to Andrew Crofts' header just after the half hour mark.
Two goals in three minutes put Forest in the driving seat, with Lansbury slotting home from the spot almost immediately after Darius Henderson had given them the lead before Nathaniel Chalobah was sent off in the 67th minute as Forest finished the match with 10 men.
Brighton went into the game having scored only four goals in their previous five matches and, in a lively start, former Newcastle winger Kazenga LuaLua provided an immediate threat for the Seagulls.
Forest were chasing a club record-equalling seventh straight win but it looked like manager Billy Davies would taste defeat for the first time in eight games when Will Buckley put the visitors back in front with five minutes remaining.
Poyet though had sympathy for the goalkeeper and said: "To begin with I thought the shot must have taken a deflection but when I've seen it again I nearly killed myself!
Billy Davies' unbeaten return as Nottingham Forest manager was preserved by an injury-time mistake from Brighton goalkeeper Casper Ankergren.
Forest were chasing a club record-equalling seventh straight win,
but it looked like Davies would taste defeat for the first time in eight games when Will Buckley put the visitors back in front with five minutes remaining.However, Ankergren, excellent until this point, allowed Henri Lansbury's shot to squirm beneath his body and their rivals shared the points.
Brighton took the lead through Leonardo Ulloa's 57th-minute strike before substitute Lewis McGugan sparked the late drama with Forest's first equaliser in the 82nd minute.
Davies' side stay fifth in the table but Albion leapfrog Leicester and move up to sixth place.