Hallé was a pioneer of hygienic reform in France, and was a catalyst towards educating others as to its importance. He created distinctions between public and individual hygiene, and initiated studies and awareness involving the multiple issues that involve hygiene, such as contagious diseases, health in the workplace, and problems associated with living in a high density urban environment, to name a few.
He was co-editor of the 1813 "Code des médicaments" (a work involving French pharmacopoeia), and made contributions to the "Dictionnaire des Sciences médicales" (Dictionary of Medical Sciences). He also carried out investigations of breast cancer, conducted research on the effects of camphor, and was a major advocate of vaccination.