Effects of antihistamines on cutaneous reactions and influx of eosinophils after local injection of PAF, kallikrein, compound 48/80 and histamine in patients with chronic urticaria and healthy subjects.

Abstract

The effects of one week's daily treatment with dexchlorpheniramine (3 + 3 mg x 2) and loratadine (10 mg x 2) on the cutaneous reactions to putative mediators of urticarial reactions were studied in healthy subjects and in patients with chronic urticaria. Biopsy specimens were taken from skin with delayed reactions and studied immunohistochemically for the presence of eosinophilic cationic protein (ECP). In healthy subjects both antihistamines significantly decreased the weal and flare induced by histamine and the histamine releaser compound 48/80. They also reduced the flare seen after injection of PAF (platelet activating factor) and kallikrein. In patients with chronic urticaria the delayed reactions to PAF and kallikrein were larger than in healthy subjects. The immediate flare seen after injection of histamine, 48/80 and PAF, and the delayed reaction to 48/80, were significantly decreased by treatment with loratadine. No correlation was found between the clinical response and test reactions. In the group of healthy subjects, eosinophils were increased in the skin of all subjects after intradermal injection of 100 micrograms of PAF and in 50% after 1 microgram of PAF, but no eosinophils were seen after injection of 1 ng of PAF. In patients with chronic urticaria the eosinophils were increased at all sites where 1 ng of PAF had been injected and also at a limited number of sites of injection of histamine, 48/80, kallikrein and saline. Treatment with the antihistamines had no effect on the influx of eosinophils in the skin.