支气管哮喘的发作可能是单一的激发因素(如螨、花粉)被吸入引起的,但这些病人的支气管对组织胺、乙酰胆碱、冷空气、运动、无抗原性尘埃及精神因素也都具有很敏感的气道反应性。动物实验和临床研究越来越多地证明气道反应性增高在支气管哮喘的发病机制中占有重要地位。健康人静脉内注射组织胺,即使剂量大到足以引起面部潮红、恶心、头痛、甚至血压下降,也未影响呼吸功能,而给哮喘病人注射小剂量组织胺、就可使其支气管收缩,肺活量减低。新近研究证明90％以上的支气管哮喘和99％以上的症状性哮喘病人的气道 The onset of bronchial asthma may be caused by inhalation of a single stimulus (eg, mites, pollen), but these patients also have bronchial sensitivity to histamine, acetylcholine, cold air, exercise, antigen-free dust, and psychiatric factors Airway reactivity. Animal experiments and clinical studies have increasingly demonstrated that elevated airway responsiveness plays an important role in the pathogenesis of bronchial asthma. Intravenous injection of histamine in healthy individuals, even at doses sufficient to cause facial flushing, nausea, headache, and even decreased blood pressure, did not affect respiratory function, and injection of low-dose histamine to asthmatic patients resulted in bronchoconstriction and decreased vital capacity . Recent studies have shown that more than 90% of bronchial asthma and more than 99% of patients with symptomatic asthma airway