A 4-month-old infant with a clear runny nose and mild cough is often due to a respiratory infection. Need to be highly vigilant for special pathogens infection. 1. Respiratory tract infection: 4 month old baby runny nose slight cough probability is caused by respiratory tract infection, if the clinical manifestation is not obvious, you can perfect blood routine to assist in the diagnosis, can be under the guidance of the doctor to be Pudilan anti-inflammatory oral solution, Peregrine granules and other drugs for symptomatic supportive treatment. 2. Gastroesophageal reflux: Gastroesophageal reflux can also appear as a mild cough, but generally will not be combined with the runny nose, you can pat the back of the baby to deal with after drinking milk. Exhaust excess air. 3. Allergy: generally speaking, 4-month-old babies due to their age, allergen determination accuracy is poor, so it is difficult to clinically clarify the possibility of allergy, can be combined with routine blood tests, if eosinophils increased significantly, need to be alert to the possibility of allergy, can be given sea saline nasal spray to deal with. Drugs need to be used under the guidance of a doctor, not private medication. If a 4-month-old baby has a clear nose and a slight cough, it is recommended to consult a doctor and follow the doctor’s instructions for targeted treatment.