Born on 30 November 1887 at McKinney, Kentucky, he graduated from Georgetown College, Kentucky in 1909 and took the MD from Johns Hopkins in 1913, where he learned surgery from Halsted and Cushing. He was appointed to the Massachusetts General Hospital, Boston, retiring as surgeon-in-chief of the Eastern Service in 1948; he was subsequently made a trustee of the Hospital. He was chiefly interested in abdominal surgery, was one of the first to develop surgical treatment for ulcer haemorrhage, and also studied neurovascular surgery. During the first world war he was on active service in France. Allen was President of the American College of Surgeons 1947-48, and chairman of its Board of Regents 1948-51. He came to London in 1947 for the 12th International Congress of Surgery and delivered a Moynihan Lecture at the College on "Duodenal ulcer", comparing the results of sub-total gastric section with those of vagus nerve interruption. The following year he presented a microtome to the Anatomy department. He came again to the College in 1950 and delivered a Hunterian lecture on "Modern trends in colonic surgery". Allen was also a foreign member of the Academie de Chirurgie and an Honorary Fellow of the Edinburgh College, and had been awarded the coveted Bigelow medal of the Boston Surgical Society. He was a popular, friendly man and a keen fisherman. He died at Boston on 18 March 1958 aged 70, survived by his wife.