Bronchial asthma is a chronic inflammatory disorder of the airways involving a variety of cells (e.g., eosinophils, mast cells, T lymphocytes, neutrophils, airway epithelial cells, etc.) and cellular components. This chronic inflammation leads to increased airway hyperresponsiveness, usually with widespread and variable reversible airflow limitation, and causes recurrent episodes of wheezing, shortness of breath, chest tightness, or cough, which often flare up and worsen at night and/or early in the morning and resolve spontaneously or with treatment in most patients. The diagnosis of asthma is not difficult based on the clinical features such as recurrent dyspnea and cough symptoms, frequent at night, relieved by medication or on their own, and croup sounds detected on physical examination. However, misdiagnosis and underdiagnosis of asthma still occur from time to time. Due to the insufficient popularity of pulmonary function tests, asthma is commonly underdiagnosed in China. For example, chronic rhinosinusitis, gastroesophageal reflux disease, recurrent viral infections of the lower respiratory tract, cystic fibrosis, bronchopulmonary dysplasia, tuberculosis, intrathoracic airway stenosis (congenital or secondary), aspiration of food, primary ciliary dyskinesia syndrome, congestive heart failure, tracheal tumors. Not all croup is asthma” is worth remembering!