The following search terms were used individually or in combination: “atopic dermatitis,” “atopic eczema,” “atopy,” “baby,” “ceramide,” “child,” “children,” “colloidal oatmeal,” “corneocyte,” “eczema,” “emollient,” “filaggrin,” “hygiene hypothesis,” “infant,” “kallikrein,” “lotion,” “neonate,” “oatmeal,” “skin surface pH,” or “stratum corneum.” Priority was given to randomized controlled trials, but clinical studies that included small groups of participants were considered for inclusion, especially if they contained data collected from infants or children. Here, KLK4 is linked to atopic eczema.