Touwaide has been a Research Fellow (Junior and Senior) of the National Foundation for Scientific Research of Belgium; a Research Assistant at the Centre for the History of Byzantine Science at the University of Louvain; an Associate Professor at the University of Provence (Aix-Marseille I), with a dual affiliation in the Department of Botany at the Faculty of Sciences in Marseille and in the Department of History at the Faculty of Letters in Aix-en-Provence; a Professor in the Department of Classics of the University of Nice-Antipolis; a Visiting Professor at the Department of History of Pharmacy in the Faculty of Pharmacy of the University of Barcelona; a Research Fellow of the Italian Institute for Philosophical Studies in Naples; a Visiting Research Professor in the unit of Byzantine History at the Center of Humanities of the National Foundation for Research of Spain; a Research Fellow at the Dumbarton Center for Byzantine Studies of Harvard University in Washington, D.C.; a Rockfeller Foundation Research Fellow at the Department of History of Science of the University of Oklahoma in Norman, OK.; a Scholar in Residence in the History of Medicine Division of the National Library of Medicine at the National Institutes of Health in Bethesda, MD; a Research Associate and, further on, a Scientific Program Administrator in the Department of Botany of the National Museum of Natural History at the Smithsonian Institution in Washington, DC.

Also, he has been a Visiting Professor at the Institute for the History of Medicine of La Sapienza University in Rome, at the University Federico II in Naples, Department of Plant Biology and Botanical Gardens, at the Second University of Naples, Faculty of Natural, Mathematical, and Physical Sciences, and at the Laboratory of Pharmacognosy at the Faculty of Pharmacy of the University of Bordeaux; a Fellow at the Wellcome Institute for the History of Medicine in London, at the Chemical Heritage Foundation in Phialdelphia, and at the Francis Wood Institute for the History of Medicine at the College of Physicians of Philadelphia; and a Visiting Scholar at the Vatican Library of Saint Louis University in Saint Louis, and at the Institute and Museum for the History of Medicine of Case Western Reserve in Cleveland.