In this study, participants will be children aged 1-5 years who have recurrent wheezing and will be allocated to one of two treatment groups, either current clinical care or airway microbiota and blood eosinophils phenotype based management for 3 months.They will be followed up for one year after the intervention. The primary outcome is the frequency of unscheduled healthcare visit for wheezing, the secondary outcome parameters are events of severe wheezing requiring oral or intravenous steroids, events of emergency department visit and hospital admissions, the changes of Test for Respiratory and Asthma Control in Kids (TRACK) score and Paediatric Asthma Caregiver's Quality of Life Questionnaire (PACQLQ) score.
Airway microbiota pattern may related the preschool asthma exacerbation. This is a single-center, randomized-controlled trial, the study will compare the management of preschool wheeze determined by airway microbiota phenotype and blood eosinophils level to the management using current clinical guidelines.