In an asthma attack the bronchioles( tiny airways in the lungs) constrict, triggering the release of histamine and other chemicals that, in turn, cause inflammation, swelling and the production of extra mucus, making it hard to breathe.

• 在哮喘发作的时，支气管(部的小气道)缩，触发释放组胺和其他化学物质，从而引起炎症、肿胀和产生特别的粘液，导致呼吸困难。