Croup is a respiratory illness that is characterized by a “barky cough” that almost sounds like a sea lion along with difficulty breathing. The breathing is the scariest part, and when it’s severe, children act and sound like they can barely get a breath in.
Yes, you’re right; croup is caused by a virus which leads to swelling of the vocal cords and the raspy voice, cough and obstructed breathing. Moist air (steamy shower room, foggy night air, or several humidifiers in the room) and staying calm is usually enough for mild croup, but severe croup can need steroids or even a trip to the ER.
Some kids will be more prone to croup, especially if they were premature and needed to be incubated with a breathing tube. Other kids just have a narrow trachea for no good reason, but regardless, most kids will grow out of it by age 6 or so. Rarely, a child will have some other sort of abnormality of the trachea (usually born with it) that will cause recurrent croup. Doctors might suspect this if your child gets croupy with EVERY cold or is having many episodes of severe croup.