Dymista, a combined product containing the antihistamine azelastine and the intranasal steroid fluticasone, provides superior clinical efficacy to both fluticasone propionate and azelastine hydrochloride in the treatment of seasonal allergic rhinitis. The superiority of efficacy not only occurs at the initiation of treatment, but persists for its duration. The mechanism underlying the superior efficacy of Dymista is not known. This trial focuses on examining the effects of Dymista on the dynamics of the allergic response in man using nasal provocation with antigen. The investigators will study the relationship between symptoms, physiology, cells and mediators.