The Effect of Provoked Allergic Reaction and Histamine on Nasal Mucosal Blood Flow in Humans

The allergic reaction in the nasal mucosa is a complex pathophysiological process with several chemical mediators involved. One of the primary mediators is histamine. This investigation was performed to study separately the effects of an allergic reaction and of histamine on the human nasal mucosal blood flow with the 133Xe wash-out method. An allergic reaction was provoked by pollen allergens and blood flow was estimated before and after provocation. In healthy subjects and in subjects with allergic rhinitis and off pollen season, the effect of histamine injected into the mucosa was studied. The allergic reaction decreased the blood flow but histamine had a converse effect in both allergic and normal subjects. This indicates that histamine alone is not responsible for the vascular effects in allergic rhinitis. Different mechanisms responsible for the decreased blood flow in the allergic reaction are discussed.