Allen was a son of George Allen, John Ruskin’s engraver, publisher and assistant. He helped George with his publishing company, but also seems to have been employed by Ruskin to assist him with his work. He travelled in Europe with him and make illustrations for him to study and use in his books. These included botanical illustrations for Proserpina and zoological studies for Love’s Meine. Ruskin also published Hugh’s drawings in Love’s Meine.

Hugh’s wife Catherine was an artist too and trained at the Slade School of Art. In addition, one of his daughters, Daphne Allen, displayed artistic talent from a young age and had her first exhibition at the age of 13. Many of her illustrations were published in children’s books and magazines such as The Tatler and an example of this work is in Sheffield’s Ruskin Collection.