What are the signs and symptoms of the infection?

Croup has a characteristic cough that sounds like a barking seal. This cough is what sets croup apart from other upper respiratory infections. Croup often begins abruptly, most often in the middle of the night. Typically, a young child will have some cold symptoms but will seem okay when put to bed. The parents are awakened in the middle of the night by the barking sound of the croupy cough. This often occurs in spasms and may even cause the child to vomit. The child often feels that he or she cannot breathe.

Often the croupy cough is accompanied by a noise called stridor. This noise is made when the child is breathing in, or inhaling. Stridor is actually a more worrisome symptom than the cough because it means that the airway has narrowed significantly. This is especially true if the child has stridor when he or she is at rest and is not upset or crying.

A child with croup may or may not have a fever.

The major risk of croup is that the child's upper airway may swell so much that the child may not be able to breathe well enough. This is called respiratory failure. As the diameter of the airway becomes more narrowed, the resistance to the flow of air increases. The child must exert more and more energy to supply enough air to his or her lungs. If the work of breathing is not somehow relieved, the child may become exhausted, go into a coma, and die. However, the majority of cases of croup do not reach this level.