Good morning, Doctor. My son 3 years old, recently, he alway cough , seriously in the night time, always wake up from sleep due to the cough, day time is better, we went to hospital, doctor auscultated, trachea and lung are ok, voice is also ok. Arround 10 days ago, he got a cold , just from that time, he started cough. His cold has already ok, no more fever, only cough is still not get well. Please tell me, what s the possiblity for this condition.