Cytokines active on eosinophils are important in the pathogenesis of allergic diseases. A study was conducted to determine if nasal eosinophilia in allergic rhinitis is associated with an increase in eosinophil-active cytokines in nasal secretions and to compare the effects of fluticasone propionate aqueous nasal spray with astemizole and placebo on the levels of these cytokines. Forty-five patients with moderately severe ragweed allergic rhinitis were randomly assigned to receive 2 weeks of treatment with fluticasone propionate aqueous nasal spray 200 micrograms once daily, astemizole 10 mg once daily, or placebo. Nasal lavage was performed in July (preseason), August (peak season), September (after 2 weeks of treatment), and October (postseason). The number of eosinophils, the amount of eosinophil-derived neurotoxin (EDN), and the amount of eosinophil survival-enhancing activity were measured. Total mean nasal symptom scores, concentrations of nasal eosinophils and EDN, and eosinophil survival-enhancing cytokine activity in nasal secretions were significantly lower after 2 weeks of treatment with fluticasone propionate compared with astemizole or placebo. Survival-enhancing activity was detected in the nasal secretions of 25 patients. By blocking activity with monoclonal antibodies, specific cytokines were identified (granulocyte macrophage-colony stimulating factor, 3 samples; interleukin-3, 2 samples; interleukin-5, 5 samples). In conclusion, eosinophil-active cytokine concentrations parallel the nasal symptoms of patients with ragweed allergic rhinitis. Unlike astemizole, fluticasone propionate significantly lowers cytokine activity in nasal tissue, which may contribute to the therapeutic efficacy of the drug.