Variations in histamine concentration in nasal secretion in patients with allergic rhinitis.

The histamine concentration and content in nasal secretion and the volume of nasal secretion in nasal washing samples were measured under different conditions in 28 patients with allergic rhinitis sensitive to birch pollen. The mean histamine concentration was significantly lower after intranasal birch pollen challenge (2.08 micrograms/ml) than in prechallenge samples (6.96 micrograms/ml), and was also significantly lower in untreated patients during the birch pollen season (2.30 micrograms/ml) than off-season (7.18 micrograms/ml). The same relationship was found between the histamine content of the secretion samples obtained on these occasions. The mean secretion volume was greater after than before challenge, but not significantly higher during the season than off-season. A partial reversion of the changes in histamine concentration and content that occurred during the season was observed during intranasal corticosteroid therapy. The concentration and content of histamine in nasal secretion from symptomatic patients after intranasal histamine challenge did not differ significantly from those in asymptomatic subjects before challenge. It was concluded that although the histamine level in nasal secretion can be used as a marker of changes in the severity of allergic rhinitis, it is not ideal for this purpose.