Mucus production may also increase, further clogging the airway. Croup most commonly occurs in young children, whose airways are much narrower than those of adults. One of the trademarks of croup is a harsh, wheezing noise that is made when air is breathed in through the constricted windpipe and over inflamed vocal cords. Fits of coughing are another characteristic symptom. Croup is usually preceded by a cold, bronchitis, or allergy attack, but can also occur if a foreign body is inhaled.
Attacks frequently occur at night.