His father, Gerhard Wallach, descended from a Jewish family that had converted to Lutheranism.

Otto Wallach went to school, a Gymnasium, in Potsdam, where he learned about literature and the history of art, two subjects he was interested his whole life.

During his work with Friedrich Kekulé in Bonn he started a systematic analysis of the terpenes present in essential oils.

Melting point comparison and the measurement of mixtures was one of the methods to confirm identical substances.

With stepwise derivatisation, especially additions to the double bond present in some of the terpenes, he achieved the goal of obtaining crystalline compounds.