Histamine level in bronchial mucus and in blood.

Antigen-induced bronchoconstriction can be brought about by provocation of either the upper or lower airways. Rising plasma histamine concentrations can be measured at the time of an increase in airway resistance and at the onset of bronchoconstriction. Relatively high histamine concentrations can be measured in the mucus from patients with chronic obstructive bronchitis. The arterial plasma concentration of histamine was significantly increased in these patients. Histamine administered to a limited area of the tracheal mucosa can induce an increase in airway sensitivity to acetylcholine, but not to allergen or histamine. The role of histamine release in antigen-induced reflex bronchoconstriction originating from the upper airway is questioned.