Table 1.

Statements on risk factors affecting development and persistence of preschool wheezing.

Question	Answer
Section 1. Pathogenesis of preschool wheezing
Q1. What is the role of infection in the pathogenesis of preschool wheezing?	There is evidence that mainly viruses can trigger wheezing in young children. RSV and HRV are the main viruses involved in wheezing pathogenesis.
Q2. What is the role of atopy in the pathogenesis of preschool wheezing?	Recurrent multi-trigger wheezing often presents a severe clinical spectrum, can be associated with atopy more frequently than EVW and might expose the child to a higher risk of developing asthma at a later age. Aeroallergen sensitization and blood eosinophils can be used as biomarkers to identify responses to ICS in a recurrent preschool wheeze.
Section 2. Risk factors for wheeze development
Q3. Does the presence of risk factors such as allergy/atopy influence the onset and the evolution of preschool wheezing?	Young children with recurrent wheezing with atopic eczema, sensitized to allergens or blood eosinophilia, are at higher risk of asthma at a later age.
Q4. Does the presence of risk factors such as previous respiratory tract infection/bronchiolitis influence the onset and evolution of preschool wheezing?	Infants with bronchiolitis represent a high-risk group for recurrent wheezing.
Q5. Does pollution influence the onset and evolution of preschool wheezing?	Traffic-related air pollution may favour wheezing, likely via a reduced response to viral infections. Both outdoor and indoor pollution can influence the respiratory health of young children from conception and birth.
Q6. Does genetics influence the onset and the evolution of preschool wheezing?	Some individuals have a genetic susceptibility and are predisposed to develop preschool wheezing at first and eventually asthma later in life. At present, little can be done to modify genetic susceptibility, but environmental exposures can be adjusted to reduce this risk and potentially work on primary asthma prevention.
Q7. Does obesity influence the onset and the evolution of preschool wheezing?	Rapid weight gain in infancy and high BMI is associated with an increased risk of wheezing in preschool age.
Q8. Do prematurity and other perinatal factors influence the onset and the evolution of preschool wheezing?	Preterm birth and low birth weight are important early life risk factors for wheezing disorders in childhood. Extremely preterm infants are at the highest risk for respiratory problems and may have lower lung function trajectories across all ages.
Q9. Does smoke exposure influence the onset and the evolution of preschool wheezing?	Maternal smoking during uterine fetal life and subsequent second and third-hand smoke exposure increase the risk of wheezing in preschool children, particularly those with a family history of allergy.
Q10. Is immunodeficiency a risk factor for the onset and the evolution of preschool wheezing?	PID must be suspected in case of persistent wheeze refractory to therapies and a history of pulmonary or systemic infections with unusual organisms. IgA deficiency can predispose the child to recurrent infections, including wheezing.
Section 3. Protective factors for wheeze development
Q11. Are probiotics protective for preschool wheezing development?	Probiotic administration to reduce wheezing development is not recommended.
Q12. Is vitamin D supplementation protective for preschool wheezing development?	Vitamin D supplementation during the winter season may decrease the risk of RTIs and wheezing exacerbations.
Q13. Is breastfeeding protective for preschool wheezing development?	Maternal breastfeeding protects from preschool wheezing.
Q14. Is influenza vaccination protective for preschool wheezing development?	Influenza vaccination is recommended for its efficacy and safety in young children ≥6 months of age with wheezing.
Q15. Are non-specific immunomodulators protective for preschool wheezing development?	Prophylaxis with non-specific immunomodulators can be considered in children with recurrent EVW to reduce the number of episodes during the winter season.