In 1910, Charles Richet suggested that studying individual variations in anaphylactic responses might both open a way to experimental investigation of the biological basis of individuality and help unify the immunological and physiological approaches to biological phenomena. The very opposite would happen however. In the next two decades, physiologists and immunologists interested in anaphylaxis and allergy experienced more and more difficulties in communicating. This divergence between the physiopathological and immunological approaches derived from discrepancies between the experimental systems used by each (...) of these scientific communities. Trying to develop a point of view that took into account all bodily reactions to stimuli, physiologists thought that individual variations between the laboratory animals they used (mainly dogs and cats) constituted important experimental data. Seeking to develop reproducible studies of infection, immunity and 'sensitisation', bacteriologists and immunologists considered that individual variations between the laboratory animals they used (mainly small rodents) constituted 'noise' and not a 'signal'. Each group's loyalty to the experimental models used in their discipline widened the gap between immunological and physiological explanations of allergies and led to the abandonment of studies on the biological basis of individuality. (shrink)