Dessau was born in Karlsuhe, which at the time was the capital of the Grand Duchy of Baden. She was related on her father’s side of the family to an ancient dynasty of Hungarian rabbis. Her mother came from a family of great culture and learning, and was a supporter of the nascent feminist movement.
Little Emma soon demonstrated her strong talent for painting. She studied art first in Karlsruhe from 1894 to 1897 and then, invited to London, at the school of Hubert von Herkommer where she became acquainted with the Pre-Raphaelites, an important artistic movement during the Victorian era.
In 1901 she married the physicist Bernardo Dessau in Karlsruhe with whom she then moved to Italy, where her husband held various academic positions until 1935. In 1902 she was among the first women admitted to attend the nude painting school of the Bolognese Academy.
Around 1905, Dessau became acquainted with the Secession Movement in German art, which was an avante garde movement that influenced the Bahaus and Art Deco styles. The name of the movement signified its break with past artistic traditions. This movement, which in part featured innovative typography, allowed Dessau to grow her woodcut art.
Her interest in this ancient engraving technique brought Dessau into contact the circle of artists that had formed around a new innovative magazine called L’Eroica, which had been founded in La Special by Ettore Cozzani in 1911. In 1912 she was thus the only woman among the many exhibitors at the first International Exhibition of Levanto set up by Cozzani’s magazine, where she presented three graphics: a Salome and two ex libris.
Her artistic output consisted chiefly of woodcut engravings and paintings, mostly portraits and nude figures. In 1917 Dessau collaborated on the monumental publication that Cesare Ratta, he great Italian print maker, dedicated to the Italian woodcuts of his time.
Dessau faced discrimination, both in Italy and Germany. During World War 1, her German origins made her an outcast in Italy. During World War 2, her Jewish origins subjected her to persecution. The Dessaus survived both world wars, but her husband died in 1949. She was an activist in the Italian Zionist movement.
Dessau continued painting and making woodcut engravings until the age of 68. She then retired to Perugia, Italy, where she lived mainly in seclusion. Some of her works are at the British Museum and in Umbria Italy.