Four-year-old baby coughing over and over again, may be caused by bronchitis, pneumonia and allergic cough. 1. Bronchitis: mainly associated with infection with bacteria, viruses, mycoplasma, chlamydia, etc. If acute bronchitis is not cured, induced chronic bronchitis, easy to cough repeatedly, the condition will recur again within a short period of time after recovery. 2. Pneumonia: when the lung tissue is invaded by bacteria and viruses, inflammatory changes will easily occur, thus causing cough, reflex cough, and the condition is easy to recur. 3. Allergic cough: related to contact with certain allergens, such as pollen, dust, animal fur, air flocculent, cold air, etc., inhalation of the respiratory tract is easy to cause recurrent cough. Four-year-old baby coughing back and forth, there may be other reasons, it is recommended to go to the hospital in a timely manner, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.