The term derives from the name of a Hungarian physician, Ignaz Semmelweis, who in 1847 discovered that childbed fever mortality rates fell ten-fold when doctors washed their hands with a chlorine solution between patients--or, most particularly, after an autopsy (at the institution where Semmelweis worked, a university hospital, physicians performed autopsies on every deceased patient). Semmelweis's decision stopped the ongoing contamination of patients--mostly pregnant women--with "cadaverous particles". His fellow doctors rejected his hand-washing suggestions, often for non-medical reasons. For instance, some doctors refused to believe that a gentleman's hands could transmit disease.
While there is uncertainty regarding the origin and generally accepted use of the expression, the expression Semmelweis Reflex has been documented and at least used by the author Robert Anton Wilson. In Wilson's book The Game of Life, Timothy Leary provided the following polemical definition of the Semmelweis reflex: "Mob behavior found among primates and larval hominids on undeveloped planets, in which a discovery of important scientific fact is punished". In section 3 of the preface to the fiftieth anniversary edition of his book The Myth of Mental Illness, Thomas Szasz describes an early exposure to Semmelweis's life and the reaction to his finding as giving him "a deep sense of the invincible social power of false truths".