croup (krōp) [key], acute obstructive laryngitis in young children, usually between the ages of three and six. The manifestations are a high-pitched cough and difficulty in breathing, owing to a spasm or swelling of the larynx. The cause can be an acute infection (especially by the influenza virus or diphtheria bacterium), an allergy, a tumor of the larynx, or obstruction by a swallowed object. Treatment depends on the cause; e.g., antibiotics are used in the case of bacterial infections, epinephrine and similar drugs in the case of allergy. The inhalation of steam from a vaporizer or hot-water faucet relieves breathing difficulties in most cases. In severe cases oxygen may be administered, or it may be necessary to cut an opening in the trachea to prevent suffocation.