Croup is a respiratory illness that causes a distinctive barking cough that sounds like a seal. Young children, especially toddlers, get croup when a virus inflames their vocal cords and windpipe, making it harder to breathe and creating that harsh, unusual cough sound.

The inflammation causes the airway to swell and narrow, which explains why children with croup sometimes make a high-pitched whistling sound called stridor when they breathe in. Parents often notice symptoms getting worse at night. Most cases are mild and can be treated at home with cool mist or steam to help ease breathing, though sometimes a doctor needs to provide medication.

While croup sounds frightening (and can certainly scare both kids and parents), it usually goes away within a few days as the body fights off the virus. Children typically become less likely to get croup by age five or six, when their airways have grown larger and are less likely to swell again.