Since both allergic asthma and allergic rhinitis are inflammatory respiratory responses, study of a nasal challenge model should help elucidate mediator release in the allergic diathesis of the lower airway. Total allergen load and "priming" are significant factors in nasal and bronchial reactivity. In IgE-mediated allergic reactions, an immediate early response is followed by a delayed response, with symptoms persisting after exposure to allergen. With immunotherapy, IgG titers rise, and the clinical response reflects a balance between the protective IgG response and the IgE-mediated allergic response. In the model studied, mast cell activation and mediator release correlated with the onset of early-phase allergic symptoms. By reducing the magnitude of mediator release and the severity of symptoms, immunotherapy may be used along with environmental controls and pharmacologic therapy to "turn off" the allergic reaction.