The former Margate midfielder arrives as the club look to end the season strongly.
Gavin Rose has been forced to act with Hamlet losing one of their loan stars.
League Two Colchester United have recalled Decarry Sheriff after a successful time at Champion Hill.
“The club would like to thank Decarrey for his goals and celebrations and wish him every success with his future career,” Dulwich said.
“Arriving is Charlie Allen, who many will remember from his time at Margate when they were promoted from the Isthmian League.
“Charlie is the son of Martin Allen began his career at Brentford whilst his father was first-team manager at Griffin Park.”