• Written informed consent has been obtained from at least one parent or legally acceptable representative (LAR), if applicable

• Infant gestational age ≥ 37 completed weeks

• Infant birth weight of ≥ 2.5 kg and ≤ 4.5 kg

• Infant postnatal age ≤ 14 days (date of birth = day 0) at enrollment

• Infant from singleton birth or infant from multiple births may if all birth siblings are enrolled.

• At least one biological parent or sibling has (or had) a medically diagnosed history of allergy, based on response to a simple screening questionnaire

• a. For the breastfed reference group only: infant is exclusively breastfed since birth with no intake of formula, and their parent(s) have the intention to continue exclusive breastfeeding until at least 4 months of age.

• or b. For the randomized formula-fed groups only: infant is exclusively or predominantly formula-fed in the 24 hours prior to enrollment, with formula feeding representing at least 75% of total daily feeds. The decision to introduce formula feeding was independently made by the parents before enrollment.

• Parents/LAR must be able to provide evidence of parental authority and identity.

• Infant's parent(s)/LAR must understand the informed consent form and other study documents and are willing and able to fulfill the requirements of the study protocol.