Two and a half year old children are always coughing, may be caused by diseases, drugs or environmental factors. 1. Diseases: diseases such as whooping cough and tuberculosis can cause atopic cough. Respiratory tract infections, upper airway cough syndrome, cough variant asthma, airway foreign bodies, gastroesophageal reflux, etc. can cause cough manifestations. 2. Drugs: relatively rare, common drugs are angiotensin-converting enzyme inhibitors, β-adrenergic receptor blockers, etc., which can cause chronic cough, and some of the children show persistent dry cough. 3. Environmental factors: some children due to atopic constitution, contact or inhalation of dust mites, cockroaches, fur, etc., can appear cough. Two and a half year old children always cough, it is recommended to go to the hospital to find out the cause and timely treatment.