Atopic dermatitis assessment
Parents were routinely encouraged to report skin concerns to the study team. Suspected cases of AD were reviewed by the blinded investigator at the earliest opportunity. Cases of AD <6 months were diagnosed based on the presence of AD, assessed either in person or via photographs when an in-person assessment was not possible. The UK Working Party Diagnostic Criteria (UKWPDC) were applied when diagnosing AD between 6 and 12 months 21. AD extent and severity were evaluated (blinded) using SCORing Atopic Dermatitis (SCORAD) for infants ≥6 months 22. During the high-level COVID‑19 restrictions, AD assessments, including SCORADs, were completed remotely by the blinded investigator using photographs and video links (see supplementary data for impact of COVID-19 on study). AD cases were treated with a standardized treatment program which included advice on emollient use and a topical steroid treatment, where required.