Croup, also known clinically as dry rales, is mainly a tone produced by airflow sounds passing through a narrowed airway, such as inflammatory exudates, congestion, and edema can narrow the airway. On auscultation it is characterized by a high-pitched sound, like the sound of a whistle, with an indefinite location, usually at the end of expiration, and the more severe the obstruction the higher the pitch of the croup. It is commonly found in the following diseases, such as bronchial asthma, chronic obstructive pulmonary disease, wheezing bronchitis, foreign body obstruction, bronchopulmonary cancer, and allergic cough, all of which are associated with croup. The main thing to do for croup is to identify the cause and take different treatments depending on the cause.