Mucosal blood flow in the human nose following local challenge with histamine

Nasal blood flow was measured using the 133Xe wash-out method in 10 non-allergic subjects and 13 asymptomatic hay fever patients. Determinations were made before and 15 min after challenge with diluent, 0.13 mg, 1.3 mg and 13 mg of histamine/nasal cavity. Nasal symptom scores were recorded. The nasal inspiratory peak flow was determined simultaneously in the hay fever patients. No differences in blood flow or symptom score recordings were found between the normal subjects and allergic patients under basal conditions or after histamine challenge. The nasal blood flow increased after challenge with the highest histamine dose. The increase was 34% (P less than 0.05) from baseline in normals and 47% (P less than 0.05) in allergics. There was a dose-dependent increase in nasal symptom scores following histamine challenge, again with no difference between normal and allergic subjects. The nasal peak flow decreased in a similar manner with a maximum decrease of 74% (P less than 0.001). The present study gives further support to the notion that histamine is not the only mediator involved in vascular reactions during allergic rhinitis.