Allhusen was the son of Henry Christian Allhusen, son of Danish-born chemical magnate
Christian Allhusen. Born in
Gateshead, he was educated at
Cheltenham College and at
Trinity College, Cambridge (matriculated 1887, B.A. 1890). He was commissioned in 1900 as a
2nd Lieutenant in the 1st Newcastle upon Tyne (Western division, Royal Garrison Artillery)
Volunteers and later served as a lieutenant in the
2nd Royal Bucks Regiment of Yeomanry and as a
Justice of the Peace for
Buckinghamshire. He did not contest Salisbury at the
1900 general election, when he was elected as the MP for
Hackney Central. He was defeated at the
1906 general election, and did not stand again. He was appointed as a
Deputy Lieutenant of
Buckinghamshire in January 1897, and was
High Sheriff of Buckinghamshire in 1913. ==Family==