NO kidding: exhaled nitric oxide fraction in preschool children.

Wheeze is one of the most prevalent symptoms in preschool children with huge impacts on children and their families, on healthcare utilisation and hence costs [1]. While most children will become asymptomatic by 5–6 years of age, some will develop asthma or, even more importantly, severe problematic asthma and/or will experience an accelerated decline in lung function. Several studies have shown that lung function in asthmatic children at 6 years of age is already reduced compared with nonasthmatic children, in particular among children with allergic asthma [2]. This impaired lung function seems to be present soon after birth in children who are at risk of asthma [3]. Hence, the preschool years and the prenatal period seem of the utmost importance if we are looking for a window of opportunity to prevent asthma or to identify those children who are at risk for severe disease.