Three-year-old baby coughing back and forth may be caused by infection, allergy, bronchial asthma and so on. 1. Infection: most three-year-old babies cough repeatedly is due to viruses, bacteria, mycoplasma and clothing protozoa and other pathogenic microbial infections, these pathogenic microorganisms can cause bronchitis, bronchopneumonia, whooping cough and other common diseases. All of the above diseases can cause coughing. 2. Allergy: When the seasons change, babies are susceptible to cold air, pollen and other stimuli of the external environment, the immune system inflammatory response, which may cause recurrent cough. 3. Bronchial asthma: the baby may also be subjected to chemical stimuli and respiratory tract infections, chronic irritation of the airways, there may be repeated coughing, wheezing and other symptoms. Three-year-old baby coughing repeatedly, you need to go to the hospital to improve the relevant examination, clear the cause of coughing after targeted treatment.