After phlegm is swallowed, there are different consequences for different patients’ constitution and the severity of their condition. For patients with poor resistance, if the respiratory infection is more obvious, a large amount of inflammatory secretions, which is phlegm, will be produced. If this sputum is swallowed, it will enter the digestive tract, which may lead to disorders of the flora of the gastrointestinal tract and also aggravate the symptoms of chronic gastritis that exist in itself, which can cause nausea, vomiting, abdominal pain, diarrhea and other symptoms. For tuberculosis caused by Mycobacterium tuberculosis infection, the patient’s sputum contains a large amount of Mycobacterium tuberculosis, and if the sputum is swallowed at this time, it may cause tuberculosis infection of the digestive system and tuberculous colitis, etc.