The effect of loratadine on activated cells of the nasal mucosa in patients with allergic rhinitis.

The effect of loratadine on the numbers of activated cells--cells expressing interleukin-2 receptors(IL-2R), HLA-DR antigens and proliferating cell nuclear antigen (PCNA)--in the nasal mucosa was studied in 48 patients with allergic rhinitis. Patients were treated with either loratadine (10 mg) or placebo for 1 month. At the end of treatment, a significant decrease in the symptom scores was noted in both groups of patients. However, the clinical score was significantly lower in the loratadine group compared to the placebo group. At the end of treatment, the numbers of IL-2R+, HLA-DR+ and PCNA+ cells were significantly decreased only in the group on loratadine. An almost significant correlation was also observed between the numbers of IL-2R+ cells and symptoms in the loratadine group. Our results show that loratadine exerts its beneficial effect possibly by inhibiting both the action of histamine and immune activation.