Acute bronchiolitis is a common, distressing illness affecting children. A virus infects the lungs, and then the airways become blocked, leading to difficulties with breathing. It is the most common reason why children are admitted to hospital, with 1-3% of all children admitted to hospital during their first winter, creating enormous strains on NHS services. The majority of those admitted with the condition are under six months of age and the associated stress for parents is considerable. After forty years of research the best treatment we have is supportive care and oxygen.