3 months baby cough throat phlegm may be whooping cough, upper respiratory tract infections, pediatric pneumonia and other diseases, need to take medication for the cause of the disease, general measures. 1. Pertussis: mainly manifested as paroxysmal spasmodic cough, can be accompanied by coughing up sputum, vomiting and other symptoms. Children with severe cough and phlegm in the throat can be treated with dextromethorphan, aminoglutethimide oral solution, aminoglutethimide hydrochloride and other cough and phlegm medications. Meanwhile, antibiotics such as erythromycin and azithromycin should also be applied as prescribed by the doctor. Secondly, the child also needs to be isolated and have balanced nutrition. 2. Upper respiratory tract infection: common symptoms include coughing, sneezing, etc. Some children may cough up a small amount of phlegm. At this time, you need to pay more attention to rest, maintain oral, nasal and pharyngeal hygiene, generally no special medication. 3. Pediatric Pneumonia: Specifically manifested as coughing, coughing up sputum, fever and other symptoms. If it is caused by Streptococcus pneumoniae infection, children need to follow the doctor’s instructions to apply amoxicillin, vancomycin and other antibiotics. At the same time, need to use saline under the guidance of the doctor to remove nasal secretions. If there is severe coughing and sputum, expectorants such as bromhexine and ambroxol should be used as prescribed by the doctor. All of the above drugs should be used under the guidance of a doctor, avoid self-medication. There are many reasons why a 3-month-old baby coughs and has phlegm in the throat, so it is necessary to go to the hospital and cooperate with the doctor to actively treat the original disease.