The common causes of cough symptoms in children are foreign body aspiration, congenital airway disease, gastro-oesophageal reflux, cough variant asthma and allergic cough, and the clinical features of each are described below. 1. Foreign body aspiration Foreign body aspiration can occur in children. About 50% of children have no witnesses at the time of foreign body aspiration, and 20% of children are seen more than 1 week after foreign body aspiration. Therefore, foreign body aspiration should be ruled out in every child with persistent cough of unknown origin, as failure to remove foreign bodies in a timely manner can lead to permanent airway damage. If the history includes a history of transient breath-holding respiratory distress, wheezing, or coughing, even if the chest x-ray is normal, foreign body aspiration should be suspected and bronchoscopy should be considered. Children with foreign body aspiration usually start with an irritating dry cough, which turns into sputum if an infection of the lungs develops. A breath-phase x-ray of the chest can help improve the diagnosis of foreign body aspiration in children. Those with abnormal medulla oblongata function can have recurrent pulmonary aspiration due to primary or secondary gastroesophageal reflux, cough due to irritation of the larynx by the foreign body, or cough due to the collection of the inhaled material in the lungs, with most clinical manifestations being an irritating dry cough. 2. Congenital airway disorders Tracheomalacia is the most common congenital airway disorder that mainly manifests as a cough, usually a barking dry cough, and parents complain that their child has been exhibiting such a coughing sound because the trachea collapses when the child’s positive chest pressure reaches enough to cause a cough. The collapse of the trachea itself irritates the mucous membrane of the airway causing coughing and causes more coughing as secretions are trapped in the distal part of the collapsed airway. The severity of tracheomalacia correlates with respiratory distress, whereas the severity of the cough does not exactly parallel the severity of the disease. When a patient presents with only a cough and no other symptoms, it makes diagnosis very difficult. Even when bronchoscopy is performed, it often fails to reveal any abnormal signs; therefore, for most patients, the diagnosis of tracheomalacia cough is based on clinical signs. 3. Gastro-oesophageal reflux (GER) In infancy, reflux is very common and the clinical course is self-limiting and usually not accompanied by cough. The occurrence of reflux in healthy children is uncommon, and some scholars in China have reported that cough due to primary gastro-oesophageal reflux accounts for only 2% of children with persistent cough for more than 4 weeks. In childhood, reflux is mainly seen in those with hypomodulation and hypotonia of the medulla oblongata, where patients develop primary or secondary inhalation-related cough due to gastroesophageal reflux; therefore, routine examination and treatment of gastroesophageal reflux is not necessary for most children with cough. 4. Cough variant asthma (CVA) and allergic cough (AC) CVA is one of the most important causes of chronic cough in children, accounting for approximately 34%-41.8% of chronic cough in children. CVA is currently considered to be a clinical subtype of asthma in which cough is the only or main clinical manifestation, and without intervention, about 1/3 of patients with CVA will develop typical asthma. the presence of airway hyperresponsiveness in patients with CVA and effective bronchodilator therapy are essential for diagnosis. The clinical presentation of AC in children is similar to that of CVA and the diagnosis of both can be easily confused, but AC patients have allergic features and do not respond to treatment with bronchodilators, whereas antihistamines and/or glucocorticoid therapy are effective.