Four months baby dry cough need to observe the baby’s specific situation, may be caused by external environmental stimulation, allergic cough and so on. 1. External environmental stimuli: If the baby is in an environment where the air is dry, the air is not fresh or there are allergens to stimulate, will show symptoms of cough. It is recommended to open the window for ventilation, improve environmental hygiene or check for allergens. 2. Allergic cough: It is a kind of cough related to contact with allergens, and children mostly show paroxysmal dry cough. Four-month-old babies have a poor sense of autonomy, parents need to closely observe, if the symptoms are serious, you need to go to the hospital in a timely manner to determine the cause of the disease to do targeted treatment.