He played college football for the South Florida Bulls and was selected by the Philadelphia Eagles in the second round of the 2010 NFL draft.

He was part of the SE Region, Peace River Conference, and played with the Cape Coral High School Seahawks.

Allen attended Cape Coral High School, where he played quarterback and threw for more than 5,000 career yards.

Also an accomplished basketball player, he averaged 15.3 points, 6.6 rebounds and 2.9 steals in 2005–2006 and was named 2nd Team All-Area.

[3] The Eagles traded quarterback Donovan McNabb to the Washington Redskins in exchange for the pick used to select Allen.

After Marlin Jackson suffered an Achilles tendon rupture during organized team activities, Allen was named the starting free safety going into training camp,[4] replacing the 2009 starter, Sean Jones.

After an impressive preseason where he only allowed 1 catch on 5 targets, he played only 5 games in the regular season, totalling 11 tackles and 1 interception.