fox-news-logoFOX NEWS Health Report by Julie Revelant — It’s frightening every time you hear it: that harsh, raspy cough that sounds like a seal barking. Chances are it’s croup— a common infection that’s usually nothing to worry about, but could be serious if you don’t know the warning signs.

Here, find out what causes croup, the signs you should look for, and how you can help your little one feel better.

What is croup?

Croup is an infection of the upper airways that causes swelling of the larynx and trachea. That swelling causes an airway obstruction, which makes it difficult for air to go in and out and results in hoarseness and the signature barking cough.

Every year, about 6 in 100 children under the age of six get croup. The infection is responsible for about 15 percent of respiratory illness in children. Typically, it affects children between the ages of 6 months and 3 years, but it can affect older children as well.

Most cases are caused by the human parainfluenza virus, which is contagious and can also cause common cold symptoms like sore throat, congestion and fever. Croup can also be caused by other viral infections, including adenovirus, measles, respiratory syncytial virus (RSV) and influenza, or by a bacterial infection, although this is rare.

When your child coughs, you may hear a high-pitched noise when he takes a breath in. This is what’s known as stridor and it can be life-threatening as it can cut off the airway, said Dr. Clifford Bassett, medical director of Allergy and Asthma Care of New York and a clinical assistant professor at New York University School of Medicine.

Some kids tend to get croup more often, either because of genetics or simply because they have a narrow upper airway.