Inclusion Criteria:  Any child with three or more episodes of parentally reported wheeze aged from 1 month to less than 6 years admitted at pediatric department of Sohag University Hospital.  Exclusion Criteria:  patients with chronic lung and congenital heart diseases. Patients with body mass index (BMI) below 3rd percentile and those ≥ 85th percentile will be excluded to avoid effect of disturbed nutritional status on vitamin D level and occurrence of wheezing.