When people’s airways inhale irritating gases or substances, they produce bronchoconstriction and symptoms of airway spasm such as dyspnea, wheezing and coughing, which is a protective response of the body. When there is a non-specific inflammatory response in the airways (asthma is a chronic airway inflammatory disease, but the airway inflammation in asthma is different from that causing general respiratory infections), the airways become more reactive to various stimuli, and their airways will also produce bronchoconstrictive responses and discomfort symptoms when they are stimulated by stimuli that normal people do not respond to, which is what we usually call airway hyperresponsiveness.