It develops in winter and spring, often secondary to upper respiratory tract infections, and occurs in children between 6 months and 3 years of age. It is prone to laryngeal obstruction causing respiratory distress. Anatomical features: 1. The laryngeal cavity of children is small and the mucosa is flaccid, resulting in obstruction of the vocal cords. The laryngeal cartilage is soft, and the mucosa and submucosa are loosely attached. 3. The laryngeal submucosa is rich in lymphatic tissue and glandular tissue. 4.Cough reflex is poor, and tracheal and laryngeal secretions are not easily discharged. 5.Low resistance and immunity. 6.The nervous system is unstable and easily provoked to laryngospasm. 7. Laryngospasm aggravates congestion and laryngeal obstruction, making the laryngeal cavity more narrow. Clinical manifestations: 1, the onset of acute daytime symptoms light night intensification. 2. Hoarseness and barking cough. 3, inspiratory laryngeal wheezing inspiratory dyspnea 4, in severe cases, trismus may appear, if not treated in time, the child’s face pale, cyanosis, confusion, and eventually died of respiratory failure. Treatment principles: 1. keep the airway open. 2. control infection. 3. apply hormones. 4. treat symptomatic tracheotomy.