[On the 100th anniversary of Clemens von Pirquet "Allergie", Muenchener medizinische Wochenschrift; 53, 1457-1458].

One hundred years ago Clemens von Pirquet's paper Allergie was published in Muencher medizinische Wochenschrift (vol. 53, 1457-1458). It was the first attempt ever made to define the term "allergy", currently considered a mile-stone in the development of contemporary allergology. The following paper presents the historical background of the event, including earlier descriptions of the diseases that later became considered allergic, as well as not-always-successful, sometimes naive, attempts to explain their causes. It also shows von Pirquet's profile, his scientific and medical achievements, especially the results of the research on reactions to second injections of antiserums and vaccines, which became the base for the presented conception of allergy, understood as body's changed reactivity. The paper describes the further evolution of this concept as well as the arisen controversy, which led to the contemporary way of understanding of this term.