Croup causes inflammation around the vocal cords (larynx) and windpipe (trachea). This swelling leads to a persistent, loud, barking cough. This is often preceded by a runny nose and a milder cough. In more severe cases, the swelling in the throat associated with croup can lead to trouble breathing. One symptom of this labored breathing may be a whistling noise, which is known as stridor, with each intake of breath. About half the time, a fever accompanies croup.