Croup is an inflammation of the larynx (voice box), trachea (windpipe), and large airways occurring in young children. The illness may begin with a runny nose, followed several days later by a harsh, barky (seal-like) cough, and hoarse voice. As the windpipe below the voice box narrows, noisy breathing (stridor) occurs as the child breathes in. Symptoms of croup often start suddenly during the night when the child awakens with a cough. Fever frequently is present.