Coughing up phlegm during a cold is not necessarily a sign of improvement. The appearance of phlegm during a cold is often considered to be related to inflammation caused by viral or secondary bacterial infections and other pathogens. Inflammatory stimuli can lead to an increase in respiratory secretions to form phlegm, when the flow of phlegm again stimulate the mucous membrane of the respiratory tract, can trigger a cough as a stress response, which will be coughing up phlegm symptoms. Coughing helps to expel phlegm from the body and is a self-protective response during the onset of a cold or other respiratory disease. Coughing up phlegm is not the basis for judging the improvement of a cold, but may also be a clinical symptom caused by various respiratory infectious diseases secondary to a cold. If the symptoms of nasal congestion, runny nose, sneezing and other symptoms are still obvious, accompanied by coughing, coughing up phlegm, sore throat and other clinical symptoms, it is considered that the condition has worsened, it is recommended to actively go to the hospital respiratory department for examination, diagnosis and standardized treatment according to the doctor’s instructions.