The fourth of five children in a family of subsistence farmers, Allen spent over a decade as a teacher and principal, before leaving education to be trained as an Adventist minister at Andrews University in the United States.

After becoming a pastor, Allen went on to serve in a number of leadership roles within the Seventh-day Adventist Church, eventually becoming the leader of the West Indies Union of Seventh-day Adventists, which had jurisdiction over Jamaica, The Bahamas, the Cayman Islands, and the Turks and Caicos Islands.

Allen became Jamaica's sixth appointed governor-general (eighth overall, including two acting governors-general).

Two years later, and following the death of his father, Allen went to Moneague Teachers' College to receive formal training in teaching.

[4][1][5] Allen returned to Jamaica to serve as a pastor, and was given increasing leadership responsibilities within the broader Seventh-day Adventist Church.

[5][A] In 1993, he returned to Andrews University, where he worked in the registrar's office while pursuing a doctorate in Educational Administration and Supervision.

[6] In his acceptance speech, Allen opined that church outreach should address the problems facing the community, including the HIV/AIDS epidemic, domestic abuse, teenage pregnancy, unemployment, and violent crime.

[6] During this time, Allen also served as the chairman of the boards of Northern Caribbean University and Andrews Memorial Hospital.

[12] On 2 September 2013, Allen became a Knight of Grace of the Venerable Order of Saint John (KStJ).