The upper respiratory tract is normally sterile and the lower respiratory tract is relatively sterile. Inhalation lung abscess, i.e., bacterial secretion from the upper respiratory tract is inhaled into the lower respiratory tract, which is less common in normal healthy adults. Specific reasons are as follows: 1, older, with basic diseases, especially cardiovascular and cerebrovascular disease patients, the pharyngeal reflex is poor, weak, cough reflex ability is poor, so it is easy to occur in this case inhalation lung abscess; 2, normal adults in the age of 65 years old, the pharyngeal reflex is weaker, so the ability to cough is poorer, at this time it is easy to appear in the upper respiratory tract bacterial secretion inhalation of the lower respiratory tract, resulting in an inhalation lung abscess 3, young adults in the state of intoxication, the upper airway protection ability is poor, easy to lead to the upper respiratory tract bacteria secretion inhalation to the lower respiratory tract, resulting in inhalation lung abscess occurs.