||We challenged 30 pollen-sensitive volunteers with allergen, recorded symptoms and signs over a 10-h period, and rechallenged them after 24 h, in order to characterize the early and late allergic symptom response in the nose. The challenge was performed after topical pretreatment with the glucocorticosteroid budesonide (200 micrograms twice daily) for 14 d and with placebo in a double-blind, cross-over trial. The early response, consisting of sneezing, discharge, and blockage, was followed by a weak late response, consisting of a few sneezes and nose-blowings, and of a sustained nasal blockage. These symptoms did not have a well-defined peak in time, and a biphasic symptom curve could not be identified. The rechallenge response showed increased nasal responsiveness. The degree of budesonide effect on the early response varied, depending on the symptom; there was a marked effect on sneezing (72% reduction; P < 0.01), a moderate effect on discharge (37% reduction; P < 0.01), and a slight effect on blockage (17% reduction of nasal inspiratory peak flow rate; P < 0.02). The degree of inhibition of the rechallenge response was similar to the effect on the initial early response. The effect on the late response was very pronounced for all symptoms and signs (97% reduction of sneezes, 76% reduction of nose-blowings, 96% reduction of blockage; P < 0.01). In conclusion, we found it difficult in the individual subject to identify a well-defined late symptom response by criteria similar to those employed to characterize the late response in the bronchi. The effect of budesonide was more marked on sneezing than on blockage, and the drug was considerably more effective on the late response than on the early response.