From 1900 he worked as a professor of general internal medicine.
He investigated metabolic and infectious diseases and explored the basic nature of bacterial toxins. In the early 1880s he conducted research on cadaveric poisons. In 1885 he was the first who isolate 1,5-diaminopentane (cadaverine). In 1890 he introduced the term toxin in his study of the toxins of Salmonella Typhimurium (the causative agent of typhoid fever).[5]
Ludwig Brieger is considered the discoverer of toxalbumin.[6]
In the colonial zone, Brieger became known for his research on arrow poisons, snake poisons and plant poisons.[7]