In 1837, Allen was one of three founding members, with James Haughton and Richard Davis Webb, of the Hibernian Antislavery Association.

Allen founded the Irish Temperance and Literary Gazette and used this publication to forward his ideas and those of the Anti-Slavery Association.

As was the case in Britain, its most prominent Irish supporters were Protestant, notably Methodists, Quakers and Unitarians, and meetings were generally held in Nonconformist churches.

[5] One of the greatest contributions to the anti-slavery debate was made by the flamboyant and controversial Irish nationalist, Daniel O’Connell, champion of Catholic Emancipation.

Allen noted that he had been visiting Dublin's Bridewell prison and considered that parts were becoming empty because of the increase intemperance.