Asymptomatic when standing and coughing when lying down may be due to allergic cough, residual inflammation of the respiratory tract and gastroesophageal reflux. 1. Allergic cough: It may be because the patient belongs to the allergic body, or is allergic to mites and dust, etc. When the patient lies down, he/she is likely to come into contact with mite debris and dust, etc., which triggers allergic cough symptoms. 2. Respiratory tract inflammation: If the patient’s respiratory tract inflammation has not been completely cured, due to the stimulation of inflammation, the residual phlegm may be deposited in the respiratory tract, and when the patient lies down and becomes horizontal, the residual phlegm can be easily discharged, and then coughing and other symptoms will occur. 3. Gastroesophageal reflux (GERD): In addition, if the patient has symptoms of GERD, the GERD may irritate the throat when lying down, resulting in symptoms of coughing. Coughing when lying down with no symptoms when standing up may also be caused by other reasons, and it is recommended that the patient go to the hospital in time for examination to clarify the cause of the disease and treatment.