PLATELET-ACTIVATING FACTOR-INDUCED IMMEDIATE AND LATE CUTANEOUS REACTIONS

In atopic subjects, intradermal injection of platelet-activating factor (PAF), 40 and 400 ng, resulted in an immediate edema reaction markedly blocked by cetirizine, 10 mg twice a day. PAF challenge also induced a significant eosinophil accumulation evidenced by a skin window technique at 2, 4, 8 and 24 h. This inflammatory phenomenon was significantly inhibited by cetirizine. In patients with chronic urticaria, PAF, 100-mu-g intradermally, induced immediate and late cutaneous reactions (LCR) also blocked by cetirizine, 10 mg twice a day. These LCR were accompanied by an infiltration of the deep dermis by degranulated eosinophils. The pathophysiological mechanism of the PAF-induced skin reactions is discussed as well as the mechanism of action of cetirizine.