What is croup and why does it occur? Croup is usually caused by a viral infection that affects the respiratory tract. It causes swelling and narrowing of the larynx and windpipe, which leads to wheezing and coughing in children. The most common cause is the parainfluenza virus, but genetic predisposition and environmental factors such as cold and dry air can also increase the risk of croup. Especially in children, respiratory [...]