[1] After treating Min Young-ik [ko], a royal relative injured during the Gapsin Coup, Allen became close to the king of Joseon, Gojong.

Allen was appointed a medical missionary and sent to China by the Board of Foreign Missions of the Northern Presbyterian Church and arrived in Shanghai on October 11, 1883.

As government law prohibited foreign religion at the time, he was appointed medical officer of the United States Legation to Korea in Seoul, thus hiding his true identity.

This event started with the assassination attempt on the life of the queens nephew, Min Young-ik [ko], who was hosting a banquet to celebrate the opening of the nation's first postal office with dignitaries including foreign diplomats and he was inflicted with 7 severe sword wounds.

Dr. Allen was summoned and treated Min's near mortal wounds, applying western medical methods against the objection of 14 of the court's medicine men.

[3] Upon hearing the wide spread rumor that a foreigner with bushy red beard revived a dead prince, many people flocked to his house.

He submitted to the Foreign Ministry "A proposal of founding a hospital for the government of His Majesty in Seoul Corea" with an introductory letter by J. C. Foulk, charge de' affair of the U.S. Legation.

Gojong granted his proposal readily and a western hospital named Gwanghyewon (廣惠院; lit.

Allen helped operate the Korean Legation and carried out diplomatic activities (his position was "foreign secretary" "참찬관" ).

Upon his return from North America he started working in July 1890 as Secretary at the United States Legation in Seoul and left 15 years later in June 1905 as the Envoy Extraordinaire and the Minister Plenipotential before his successor Morgan closed the United States legation in November 1905.