EFFECT OF CETIRIZINE AND PREDNISOLONE ON CELLULAR INFILTRATION AND CYTOKINE MESSENGER-RNA EXPRESSION DURING ALLERGEN-INDUCED LATE CUTANEOUSRESPONSES

Background The ability of cetirizine to inhibit eosinophil infiltratio n into the sites of allergen-induced cutaneous late-phase reactions is controversial. A previous skin biopsy study gave negative results wit h 15 mg of cetirizine as a single dose. Objective To confirm these fin dings we have used cetirizine (30 mg daily) for 5 days and compared th e results with prednisolone (20 mg daily for 5 days) as a positive con trol. The effect of these agents on mRNA positive cells for interleuki n-3 (IL-3), interleukin-4, interleukin-5 and granulocyte/macrophage-co lony stimulating factor (GM-CSF) was also evaluated. Methods A double- blind, placebo-controlled cross-over study (n = 12) was followed. Afte r each treatment 30 biological units (BUs) of Dermatophagoides pterony ssinus or Phleum pratense were injected intradermally and the early (1 5 min) and late-phase response sizes (6 and 24 h) were measured. Skin biopsies were taken at 24 h for immunocytochemistry and in situ hybrid ization. Results Cetirizine but not prednisolone inhibited the early-p hase response (37%, P = 0.004). In contrast prednisolone, but not ceti rizine, significantly inhibited the size of the late-phase reaction at 24 h (70%, P = 0.021). This was associated with significant decreases in total (MBP+) and activated (EG2+) eosinophils (P = 0.019 and 0.014 , respectively), as compared with placebo. There were also clear but n on-significant reductions in interleukin-3, interleukin-4, interleukin -5 and granulocyte/macrophage-colony stimulating factor mRNA+ cells. C onclusion Prednisolone, but not cetirizine, inhibited both the magnitu de of the allergen-induced late-phase response and the accompanying lo cal eosinophil infiltration. These corticosteroid effects were associa ted with a reduction in cells expressing mRNA for 'TH2-type' cytokines .