 After a postgraduate course at the universities of Vienna, Würzburg, and Paris he settled in Berlin, where he practised as a specialist first in otology, and later in dermatology and syphilis.In 1862 Lewin was admitted to the medical faculty of his alma mater as privat-docent in otology.In 1865 he became chief physician in the department of dermatology and syphilis at the Charité Hospital, and in 1868 was appointed assistant professor.