Behavior and clinical relevance of histamine and leukotrienes C4 and B4 in grass pollen-induced rhinitis

The release kinetics of histamine and leukotriene C₄ (LTC₄) and B₄ (LTB₄) were investigated in nasal secretions of 10 patients with hay fever after antigen challenge. High levels of biologically active histamine were found in nasal washes from asymptomatic allergic and normal subjects. With repeated lavages, the amount of histamine recovered dropped markedly. Grass pollen challenge was followed by a significant (p <0.05) dose-dependent and time-limited (5 min) increase in histamine level in 7 of 10 patients; these values, however, were lower than those found in basal conditions. In 8 of 10 patients with hay fever, antigen challenge induced a significant (p <0.05) dose-dependent increase in LTC₄ level, which persisted for 30 min. The LTC₄ generation was well correlated with the appearance of allergic symptoms; LTB₄ production was found in 2 patients only. A different pattern of symptoms was observed after in vivo nasal stimulation with histamine and LTC₄. Histamine caused sneezing, itching, rhinorrhea, and nasal obstruction; conversely, the main symptom induced by LTC₄ was a more pronounced and longer lasting nasal obstruction.