Jozef Jadassohn is the father of patch testing - At the time of his discovery in 1895, he was Professor of Dermatology at Breslau University (now Wroclaw in Poland). He initially reported a patient who had developed an eczematous reaction to mercury plasters. He recognized the potential for eczematous reactions to occur in some (sensitized) patients when chemicals were applied to their skin; he thereby introduced the world to the contact test, and then referred to as "Funktionelle Hautprufung".
Bruno Bloch (Professor at Basel and Zurich Universities) is considered by the international community as one of the more outstanding pioneers in the field of patch testing, continuing, and expanding Jadassohn's clinical and experimental work. In some textbooks and papers, patch testing is sometimes quoted as the Jadassohn-Block technique.
In retrospect, it is difficult to assess the real place of the patch test procedure for the diagnosis of contact dermatitis between 1895 and the 1960s. Some points seem obvious
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