(¤ 1850, † 1929) Born in Hamburg in 1850 as the son of a general practitioner. Studied medicine in Heidelberg from 1870. Doctorate in 1875 under Waldeyer. Until 1884, various positions, including with his father in Hamburg. 1882 Founded the "Monatshefte für praktische Dermatologie" together with O. Lassar and F. Hebra. 1881 Foundation of his own dermatological clinic. 1887 First description and clinical delineation of seborrheic eczema. 1890 First description of parakeratosis variegata, clear clinical differentiation from other diseases of the parapsoriasis group. 1889 Together with Taenzer, first description of Ulerythema ophryogenes. 1890 together with Pollitzer and Janovsky, first description of acanthosis nigricans. Unna, together with Beiersdorf and Troplowitz, introduced ichthyol into the therapy of skin diseases. This joint venture also gave rise to Nivea, which is still marketed unchanged today.
In 1907, the city of Hamburg awarded him the title of professor. In 1919, he was appointed dermatology professor at the newly founded University of Hamburg.