A child, most often between the ages of 6 months and 3 years (peak incidence 1–2 years, rarely seen >6 years), arrives with a characteristic barking cough that sounds very much like the bark of a seal. The patient may arrive with reports of having significant difficulty breathing in the middle of the night. There is usually a prodrome of low-grade fever and symptoms of a mild upper respiratory infection. The barking cough tends to occur at night, with symptoms worsening on the second night.

 

The parents are usually alarmed by the sound of the cough or the child’s breathing difficulty. The throat is clear and normal in appearance, and there may be varying degrees of stridor (predominately inspiratory) or retractions of the accessory chest muscles.