PCLAF and anaphylaxis: They concluded that a failure of PAF acetylhydrolase to inactivate PAF may contribute to the severity of anaphylaxis on the basis of the following observations: (i) serum PAF levels were directly correlated with anaphylaxis severity, (ii) serum PAF acetylhydrolase activity was inversely correlated with anaphylaxis severity and (iii) PAF acetylhydrolase activity was significantly lower in patients who had fatal anaphylactic reactions to peanuts than in controls (Vadas et al, 2008).