Allen has appeared in many sketch shows, including We Know Where You Live (Channel 5), Smack the Pony (Channel 4), Goodness Gracious Me and The All Star Comedy Show. She has also appeared in many television dramas including Dalziel and Pascoe and Coronation Street, as well as the sitcom Happiness alongside Paul Whitehouse. Subsequently she appeared as Sandra, in the film version of the Viz comic strip The Fat Slags, and as a panelist on one episode of Mock the Week.
Allen appeared in the first episode of the second series of the E4 teenage drama Skins, playing Maxxie's mum Jackie Oliver. She also appears in BBC drama Waterloo Road as Georgia Stevenson.