Some patients with asthma do present with chronic cough and chest tightness without significant wheezing, but with increased airway reactivity, which is now called “cough variant asthma”. Since the smooth muscles of the airways of asthmatic patients are not in a constant state of contraction and diastole, the diagnosis of asthma requires the assistance of medication, which leads to the bronchial provocation test, especially for patients with atypical signs and symptoms, or patients with a history of suspected asthma, who are in remission and whose lung function is still within the normal range. Usually, the bronchial provocation test uses drugs such as histamine or acetylcholine, which can cause contraction of bronchial smooth muscle, and then use lung function as an indicator to determine the degree of bronchial stenosis, thus reflecting the degree of increased airway reactivity. Airway hyperresponsiveness is the most important feature of bronchial asthma, so a positive bronchial excitation test can help diagnose asthma.