Clinical Research Directory

Inclusion Criteria: Each participant must meet the following criteria to be included in this study: * Healthy, term (born no earlier than 2 weeks before estimated date of delivery), predominantly breastfeeding infants aged 6 to 12 weeks (inclusive) who are expected to be predominantly breastfed for at least 6-months. This will be determined by answering yes/no to question 'do you intend/wish to breastfeed until your infant is at least 6 months of age.' Up to one bottle (approx. 120mL) of formula per 24 hours at the time of screening is acceptable, as this will contain \<100 IU vitamin D. * Has a parent/legally acceptable representative (LAR) capable of understanding the informed consent document and providing consent on the subject's behalf, * The parent must expect to be able to complete 4 online questionnaires over the infant's first 12 months of life and for the infant to be available for skin prick testing (+/- food challenge) at The Royal Children's Hospital at 12 months of age. Exclusion Criteria: Participants meeting any of the following criteria will be excluded from the study: * Infants who are currently receiving vitamin D supplementation * Infants on medication that interferes with vitamin D metabolism * Poor health due to a current or past significant disease state or congenital abnormality. * Prematurity \<37 weeks/low birth weight \<2500 g/Small for gestational age (SGA) * Unable to provide consent without the aid of an interpreter. * Women at high risk of vitamin D deficiency with infants on vitamin D supplementation.