PCLAF and allergic disease: The half-life of PAF in a study involving patients with acute allergic reactions was found to be ∼13.6 min in serum with the lowest PAF acetylhydrolase activity, ∼6.0 min in serum with intermediate PAF acetylhydrolase activity, and ∼3.8 min in serum with the highest PAF acetylhydrolase activity (59).