DefinitionCroup is breathing difficulty accompanied by a "barking" cough. Croup, which is swelling around the vocal cords, is common in infants and children and can have a variety of causes.Alternative NamesViral croup; Laryngotracheobronchitis - acute; Spasmodic croupCauses, incidence, and risk factorsViral croup is the most common. Other possible causes include bacteria, Allergies, and inhaled irritants. Acid reflux from the stomach can trigger croup.Croup is usually (75% of the time) caused by parainfluenza viruses, but RSV, measles, adenovirus, and influenza can all cause croup.Before the era of immunizations and antibiotics, croup was a dreaded and deadly disease, usually caused by the diphtheria bacteria. Today, most cases of croup are mild. Nevertheless, it can still be dangerous.Cr