['This study evaluated risk factors for acute wheeze in preschool children and investigated whether subnormal levels of vitamin D were associated with increased risk for acute wheeze, atopy or viral/bacterial respiratory infections.', 'We recruited 130 children with acute wheeze, aged 6\xa0months to 4\xa0years, from paediatric emergency departments in Stockholm, Sweden, and 101 age-matched controls with no history of wheeze or sensitisation to airborne allergens. Parents answered standardised questionnaires, and blood samples were analysed for specific IgE to airborne and food allergens and levels of 25 hydroxyvitamin D (25(OH)D). Nasopharyngeal virus samples were collected during the emergency department visit in the group of children with wheeze, and a subset were also tested for bacteria.', 'Vitamin D insufficiency (25(OH)D\xa0<\xa075\xa0nmol/L (30\xa0ng/mL)) was associated with an odds ratio of 2.7 (95% confidence interval 1.1-6.2) for acute wheeze. However, no association was found between vitamin D insufficiency and atopy, presence of virus or bacteria or recurrent infections. Children older than 24\xa0months were particularly at risk of subnormal vitamin D levels, irrespective of wheezing history.'] Are subnormal levels of vitamin D associated with acute wheeze in young children?