Wheezing in preschool children is one of the most commonly presented symptoms in everyday pediatric practice 1 occurring in a third of children by their third birthday and half of children by 6 years. The prevalence of parent reported wheeze in 2-year-old children was 2–17% in the European EuroPrevall birth cohort study. Preschool wheeze (PSW) is associated with significant healthcare resource utilization, accounting for approximately 75% of all childhood hospital admissions for acute wheeze and associated with significant impact on family quality of life. 2
PSW has been classified in several different ways, based on time of appearance, natural history, comorbidities, and triggers. Some of these children with different phenotypes of wheezing will develop asthma later in life. However, until the diagnosis is confirmed, decision making regarding the proper treatment is uncertain and challenging. 1
PSW can be described as a multifactorial disease influenced by various genetic and environmental factors. Early viral infections, bacterial colonisation and allergen sensitisation are among the most important in causing wheeze and the subsequent development of asthma. These early life exposures, together with genetically determined susceptibility, can affect the immune system early in life with a major impact on the natural history of the disease. 3