The effect of topical fluticasone propionate on intranasal histamine challenge in subjects with perennial allergic rhinitis.

The mechanism of action of topical intranasal steroids is obscure. To investigate this, we have studied the effects of a topical intranasal corticosteroid, fluticasone propionate on nasal airflow resistance (Rnaw), secretions, cytological smears and symptoms. Fluticasone propionate aqueous nasal spray was given to 11 patients with perennial allergic rhinitis in a double-blind, placebo-controlled study. On each day, patients were challenged with ascending doses of histamine. Rnaw, secretion volume, total protein, mucin, lysozyme and albumin were measured. Nasal smears were taken and sneezes counted. Diary card data were collected for both treatment periods. There was a significant, dose-related increase in Rnaw and sneezing on histamine challenge. A single dose of fluticasone had no effect on any parameter. After 4 weeks of treatment, resistance measurements were reduced (post-challenge g.m.2.8 cmH2O/l/s, Q1-Q3 1.6-4.8; placebo 4.2, 2.9-5.3: P < 0.0001) as were baseline secretion volumes (mean 2.4 ml/5 min, c.i.1.9-3.0; placebo 3.3, 2.8-3.8: P < 0.05). Eosinophil counts were suppressed (fluticasone 5.8%, c.i. 4.0-15.7; placebo 23.3%, 12.4-34.1: P < 0.05) and the composite symptom score reduced (P < 0.05). Fluticasone has long-term effects on the nasal response to histamine in perennial allergic rhinitis and part of this effect is likely to be vascular.