The nasal antiinflammatory effects produced by maintenance treatment with topical steroids include reduced production of cytokines. The present study explored nasal mucosal effects induced during the first 9 h after a single dose of topical budesonide. Nine subjects with allergic rhinitis due to birch or timothy pollen were given budesonide (256 microg; Rhinocort Aqua) or placebo in a double-blind, randomized, crossover (4 wk washout) manner. Nasal allergen challenges were performed 30 min after the steroid/placebo pretreatment. Before and 30 min, 1, 3, 5, 7, and 9 h after challenge, filter paper strips were placed on the nasal septum and inferior turbinates for 10 min to sample undiluted mucosal fluids. Strips were then extracted in 1 ml buffer for cytokine analysis (ELISA). Allergen challenge produced acute nasal symptoms that peaked at 30 min and then tapered off. Conversely, both GM-CSF and IL-5 were increased only at 3, 5, 7 and 9 h (p < 0.05 compared with baseline). Budesonide did not affect the nasal symptoms but inhibited (p < 0. 05; compared with placebo treatment) the allergen challenge-induced mucosal output of GM-CSF and IL-5. These data demonstrate that GM-CSF and IL-5 are induced in a nonsymptomatic, late phase response to nasal allergen challenge, and that this cytokine response is prevented by single dose budesonide pretreatment.