The contributions of Paul Ehrlich to infectious disease.

Paul Ehrlich (1854-1915) is nowadays considered a pioneer in a number of medical fields, and in the course of time his role in the establishment and development of disciplines such as histology, immunology, oncology and haematology has been acknowledged. Aim of this historical note is to illustrate, in the area of chemotherapy, the special importance of this brilliant scientist whose 150th anniversary of birth occurred in 2004. Already as a medical student, Ehrlich was obsessed by structural organic chemistry and dyes, and, continually studying these issues, he elaborated his theory regarding the discovery of a "magic bullet", able to specifically destroy tumour cells and micro-organisms. In practice he applied methylene blue to the treatment of malaria patients, following his intuition that such a dye could destroy parasites. However, his culminating achievements in the chemotherapic field, reached even at the expense of his health, were the concept of the one-dose treatment of Helicobacter pylori infection, and the creation of arsphenamine (compound 606, or Salvarsan), the first really effective compound in controlling human syphilis. Within the many and various contributions of Ehrlich to the development of experimental and clinical medicine, a special mention of his experimental studies and clinical applications in the area of chemotherapy is essential, since his achievements in this biomedical area remain a paramount legacy in the history of the therapy of infections.