Walnut, cashew, and peanut proteins in household dust and sensitization in young children with atopic dermatitis

Walnut, cashew, and peanut proteins in household dust and sensitization in young children with atopic dermatitisTo the Editor, Tree nut and peanut allergies are increasingly recognized in young children, 1,2 with geographic variation in the predominant causative allergens.3 In Japan, walnut, cashew, and peanut have been reported to cause allergic reactions, including severe reactions, even in children aged ≤2 years. 2 Higher household peanut consumption is associated with higher peanut protein concentrations in household dust (HD), and earlylife environmental peanut exposure has been associated with peanut sensitization. 4 However, evidence regarding tree nut proteins in HD is limited.Higher walnut protein levels in bed dust have been reported in children with Jug r 1 sensitization.5 Few studies have examined cashew protein in HD.We therefore investigated the associations between HD concentrations of walnut, cashew, and peanut proteins and sensitization to the corresponding allergens in children with atopic dermatitis (AD).This multicenter case-control study included children aged ≤3 years with current or past AD who had never consumed walnuts, cashews, or peanuts.Blood sampling was performed as part of routine clinical care, and only children who underwent blood sampling were eligible for screening.Sensitized cases were defined using predefined allergen componentspecific IgE thresholds: Jug r 1 ≥ 0.98 UA/mL for walnut, Ana o 3 ≥ 2.00 UA/mL for cashew, and Ara h 2 ≥ 4.71 UA/mL for peanut, corresponding to a positive predictive value of ≥95%.[6][7][8] Controls had Jug r 1, Ana o 3, and Ara h 2 levels <0.10 UA/mL and no history of food allergy (FA).Children with component-specific IgE levels between the case and control thresholds were not eligible.All eligible participants whose guardians provided written informed consent were enrolled between 2022 and 2025.The study protocol was approved by the Ethics Committee of Yao Municipal Hospital (approval number: R-04-14).