The cold cycle is usually divided into pre-cold, early cold, mid-cold and late cold. A. The pre-cold period is also known as the incubation period, when the human body’s symptoms are not obvious, but the virus of the cold has been latent in the human body’s bloodstream, when the clinical symptoms of physical weakness, head pain will appear. Second, the early stage of the cold when the clinical symptoms appear in the performance of sore throat, swallowing discomfort, dry throat, rough feeling in the throat, mild painful swallowing, usually last 1-2 periods. Third, the middle of the cold is the most obvious moment of cold symptoms, when sneezing, nasal congestion, fever, mental discomfort, headache, drowsiness and other situations occur. Fourth, in the late stage of the cold will appear cold symptoms alleviated, but there is also peripheral weakness, loss of appetite, dizziness, headache and other clinical symptoms appear.