Croup, a term used in Scotland from an early period to describe a certain train of laryngeal symptoms, was first applied by Dr Francis Home, in 1765, to an acute inflammatory and non-contagious affection of the Larynx (q.v.), in which there is the formation of a false membrane or fibrinous deposit on the mucous surface of the windpipe. The invasion of the disease resembles that of simple Catarrh (q.v.), and may be very insidious. The child is languid, feverish, and thirsty, and a dry, shrill cough is gradually developed, but these symptoms sooner or later give way to those of the second stage. Here the respiration becomes difficult, the drawing of each breath having a hissing and 'croupy' sound; the voice is almost inaudible or greatly modified, and accompanied by a harsh, brassy, or may be stifled cough; the face is red and swollen, and covered with sweat; and the nostrils are rapidly working. If the little patient is not relieved by coughing or vomiting up some membranous shreds and glairy mucus, a state of greater dyspncea ensues; the lips become livid and the nails blue; the fever is higher, the pulse quicker but weaker; and the child's efforts to relieve the increasing obstruction to the breathing are most distressing to witness. A period of extreme restlessness and suffering is (unless relieved by immediate treatment—see below) soon followed by death from increasing coma, syncope, or exhaustion.
Croup seems to be caused by a damp atmosphere of low temperature, and is got in exposed situations. It is most frequently met with between the years of two and ten, although all ages and classes are liable to suffer from it. It is commoner in boys than girls. Croup requires to be distinguished from simple catarrh of the windpipe; from so-called false croup, a spasmodic affection of the larynx—the Laryngismus Stridulus of Dr Mason Good; and from Diphtheria (q.v.), an infectious disease in which a false membrane is usually found on the pharynx or palate, as well as in the larynx. As croup is an acute and very fatal disease, the treatment requires to be active and decided. If the case is seen early, apply an ice-bag to the throat and give ice to suck, but if you suspect the presence of false membrane, give a full dose of an emetic, such as ipecacuanha, sulphate of copper, or sulphate of zinc, which should be repeated in three or four hours if necessary and effectual in relieving the breathing. The child should at intervals be placed in the hot bath, and inhalations of steam or medicated vapours administered. An inhalation of lactic acid is often of great use in the first stage. If these means fail, Tracheotomy (q.v.) must be at once resorted to, to save the life of the patient, as recommended by Trousseau.