The claim was criticized as lending support to blood libel, an allegation that modern historians have described as unsupported by facts and which the Catholic Church has similarly repudiated since the 13th century.
La cucina ebraica in Italia dal Rinascimento all'età moderna (Eating Jewish style.
Ebrei d'Europa e omicidi rituali ("Passovers of Blood: The Jews of Europe and Ritual Murders"), was published in February 2007.
[8] The book was much criticized for providing material that anti-Semites might capitalize on, though Sergio Luzzatto praised his intellectual courage in reopening a dossier that had lain under a taboo.
That said, the possibility existed that: certain criminal acts, disguised as crude rituals, were indeed committed by extremist groups or by individuals demented by religious mania and blinded by desire for revenge against those considered responsible for their people’s sorrows and tragedies.
His book examines the strong documentary evidence in medieval medical handbooks that dried human blood, traded by both Jewish and Christian merchants, was thought to be medicinally efficacious.
Under the stress of forced conversions, expulsions and massacres, Toaff thinks it possible that in certain Ashkenazi groups dried human blood came to play a magical role in calling down God's vengeance on Christians, the historic persecutors of the Jews, and that this reaction may have affected certain forms of ritual practice among a restricted number of Ashkenazi Jews during Passover.