The mucous membrane of the larynx, trachea, and bronchial tubes becomes inflamed and swollen and produces excessive mucus. Laryngotracheobronchitis is synonymous with croup.
Respiratory infections caused by various kinds of virus can often result in croup.
However, a more serious but less common kind of croup, called membranous croup, may occur as a symptom of diphtheria. This condition is a medical emergency. Rest is important. A vaporizer is an extremely important aid to breathing. If a vaporizer is unavailable, create a steamy environment in the bathroom by running a hot shower.