The hosts' Anthony Quinn was ordered off in the 59th minute, conceding a penalty which McAllister ruthlessly despatched. The same player added a second but Fraser McLaren was denied a third by fine Blair Lochhead save.
Second-placed Annan Athletic lost 2-1 at home to Stirling Albion. David Weatherston had Stirling 2-0 up before Blair Henderson hit back with a 76th-minute penalty.
Clyde remain third after a 4-2 victory away to East Stirlingshire. Clyde led 2-0 through Keiran MacDonald and Stefan McCluskey before Brian McQueen's own goal reduced the deficit.
However, Michael Daly's header made it 3-1 and McCluskey added a fourth in spectacular fashion. Kevin Turner got a last-minute second for East Stirling.
Berwick Rangers kept their play-off hopes alive with a composed 3-1 home win over Albion Rovers.
Paul Currie, Ross Gray and Scott Dalziel all netted for Berwick before Ryan Donnelly pulled one back.
Montrose slipped to a 3-0 loss at home to Elgin City, whose goals came from Shane Sutherland and an Adam MacLeod double.