Career
Outside refereeing Allaerts works as an Information Technology manager. Allaerts began refereeing in 1985 and took charge of his first Belgian First Division game in 1996. He was named the referee for the first Group B game of the Union of European Football Associations Cup 2008-2009 season between Hertha Berlin and Benfica in Germany, on 23 October 2008, along with Danny Huens and Joel De Bruyn as his linesmans, and Jean-Baptist Bultynck as the 4th referee.
In the 2008-2009 season he refereed 18 games in the Belgian First Division.
In total he showed 79 yellow cards and 4 red cards and awarded eight penalties. Furthermore, in 2008-2009 he refereed one game in the Champions league between Football Club Basel and Sporting Clube de Portugal.