Based on more recent nasal allergen challenge studies (Scadding et al, unpublished data; mean 4.63, standard deviation 1.65 for AUC 0-60 minutes post grass pollen nasal challenge in 14 allergic volunteers), inclusion of 13 patients per group will provide 80% power to detect a 40% reduction in AUC after challenge, whereas inclusion of 22 patients per group will provide 80% power to detect a 30% reduction.