Since then, several lines of evidence attested to this mechanism of anaphylaxis [59], including the finding that C depletion and production of C3a and C5a in human anaphylaxis correlated with the severity of the reactions, and the induction of immediate wheal-and-flare reactions after intradermal injection of anaphylatoxins in healthy volunteers [52, 60–62]. This evidence concerns the gene C3 and anaphylaxis.