There are many reasons for coughing while lying on the left side, which may be caused by chronic pharyngitis, chronic bronchitis, heart failure and so on. 1. Chronic pharyngitis: due to the presence of chronic inflammation in the throat area, lying on the side can produce pressure on the neck, resulting in irritation of the throat area, and then irritating cough, is one of the more common causes. 2. Chronic bronchitis: when lying on the side of the lungs to produce pressure, resulting in tracheal pressure, the presence of inflammation itself, can produce stimulation and cough performance. 3. Heart failure: lying on the left side of the heart can produce extrusion, resulting in lung bruising and other conditions, which in turn produces irritating cough. There are many reasons for lying on the left side of the cough, it is recommended to go to the hospital in a timely manner to clarify the cause of the disease, and follow the doctor’s instructions to standardize the treatment.