Nasal allergen challenge procedure
A first nasal allergen challenge was performed to titrate the allergen
dose eliciting a positive response. Briefly, nasal allergen challenge
was performed as previously described by administering increasing doses
of a grass pollen allergen extract (Stallergenes Greer) every 10 minutes
by means of a nasal pump spray delivery device (14). A Lebel score
> 5 was considered as a positive response (15). After a
washout period of 4 weeks, patients underwent two nasal allergen
challenges with either a single threshold dose of the grass pollen
allergen extract (Stallergenes Greer) or a diluent (saline solution) in
a randomized order at least 4 weeks apart. All the challenges were
performed outside the grass pollen season, and none of the subjects was
exposed to any other relevant respiratory allergens.