Acute bronchitis occurs mainly during microbial invasion, exposure to physical and chemical factors, and in the presence of an allergic reaction of the organism. 1. Microbial invasion, such as when the body is infected with common viruses of the upper respiratory tract, such as adenovirus, influenza virus, coronavirus, rhinovirus, herpes simplex virus, respiratory syncytial virus and parainfluenza virus, as well as bacterial infections of the upper respiratory tract, such as Streptococcus pneumoniae and C.pneumoniae, acute bronchitis will occur. 2. Exposure to physical and chemical factors, such as when the patient is exposed to cold air, dust, irritating gases or smoke, can cause acute injury and inflammatory reaction of the bronchial mucosa. 3. The occurrence of allergic reactions, such as the body inhalation of pollen, dust, fungal spores and other allergic substances, will cause the body allergic reaction, resulting in acute bronchitis. Patients with acute bronchitis should seek timely medical treatment and active treatment.