The comparison of 4 cases of immediate anaphylactic death following the intramuscular injection of antibiotics (different types of penicillin or cephalosporins) with 4 cases of immediate non-anaphylactic death (induced by different causes) recognized splenic eosinophilia, as the main feature for the differential diagnosis, in agreement with isolated previous studies. The use of a stain (pagoda red) little known and seldom employed in Pathology and in Forensic Medicine, showed the concomitant massive presence (immunohistochemically confirmed) of mast cells and degranulated mast cells, the latter mainly located in splenic sinuses. The whole of our findings led us to consider the spleen as the possible shock organ in man. Waiting for further judgment on our hypothesis, we seized the opportunity to remark the employment of the pagoda red stain when the contemporary demonstration of eosinophils, mast cells and degranulated mast cells is required.