Effect of cetirizine on cutaneous reactions to PAF, kallikrein and serum in patients with chronic urticaria.

The effects of oral administration of the antihistamine cetirizine on the weal and flare caused by intradermal injection of platelet activating factor (PAF-acether), kallikrein, histamine and the patient's own serum were investigated in 10 patients with chronic urticaria. Cetirizine markedly reduced the weal and flare induced by all these agents as measured 12 min after the injections. The delayed reactions observed after injection of PAF, kallikrein and serum were also inhibited by cetirizine at 6 hours. In addition, reactions which were present 20 h after injection of the agent before administration of cetirizine were found to be inhibited at the same point in time after cetirizine treatment. These effects might explain the good inhibitory clinical effect of cetirizine on the patients' urticaria. No side-effects were noted during the treatment.