Kangmo Ahn

Background: The mechanisms underlying distinct food allergy (FA) trajectories in children remain unclear. This study aimed to classify FA trajectories and examine differences in placental DNA methylation and serum cytokine profiles. Methods: A total of 1518 children from the COCOA (COhort for Childhood Origin of Asthma and Allergic Diseases) study, followed until age 7, were classified into FA trajectories using group‐based trajectory modeling. Serum cytokine levels were measured at ages 3 and 7 years. Placental methylation profiling was performed with Infinium MethylationEPIC BeadChip. Results: Children were classified into four trajectories: no FA (87.3%), early remission (6.9%), early persistent (4.6%), and late remission (1.1%). At ages 3 and 7, the early persistent FA trajectory exhibited higher interleukin (IL)‐4, IL‐5, and IL‐6 levels than the no FA trajectory. At age 3, IL‐10 levels were lower in the early persistent trajectory than in the late remission trajectory. In DNA methylation analysis, the Ribosomal Protein S6 Kinase A2 (RPS6KA2) and Germinal Center Associated Signaling And Motility Like (GCSAML) genes were significantly hypermethylated in the early persistent FA trajectory compared to the no FA and early remission trajectory ( p < 0.05). GCSAML methylation was positively correlated with total IgE, egg white–specific IgE, early‐life eosinophils, and IL‐5 at age 7 (all p < 0.05). Conclusion: Hypermethylation of RPS6KA2 and GCSAML, reduced IL‐10 levels, and elevated Th2 cytokines were associated with early persistent FA trajectory, potentially influencing its allergic inflammation and persistence.

Background/Objectives: The World Health Organization recommends continued breastfeeding for up to 2 years of age. However, because breast milk contains less iron than formula milk, prolonged exclusive breastfeeding may increase the risk of iron deficiency anemia. This study aimed to compare iron status and growth outcomes at 12 and 36 months based on feeding methods during the 6–12-month period. Methods: In this prospective birth cohort study, we followed 126 children from birth to 36 months. Participants were categorized into breastfeeding (BF, n = 21), formula feeding (FF, n = 62), and mixed feeding (MF, n = 43) groups according to milk feeding over 6–12 months of age. Anthropometric measurements and iron parameters were compared among groups at 12 and 36 months. Results: At 12 months, the BF group had significantly lower weight and height compared to the MF group. Hemoglobin, mean corpuscular hemoglobin, and mean corpuscular hemoglobin concentration were significantly lower in the BF group than in the FF and MF groups, while red cell distribution width was significantly higher in the BF group. At 36 months, no differences in anthropometrics or iron parameters were observed among the groups. Conclusions: Infants breastfed without formula from 6 to 12 months showed lower iron-related hematologic parameters at 12 months, which largely resolved by 36 months. These findings highlight late infancy as a potentially vulnerable period for insufficient iron intake and support the importance of adequate iron supplementation and timely introduction of iron-rich complementary foods during this critical developmental stage.

To investigate the effect of early feeding type on gut microbiota composition and atopic dermatitis (AD) development in cesarean-delivered infants, and to evaluate whether probiotic-supplemented formula can mitigate microbial and immunologic disadvantages associated with cesarean delivery. A total of 129 infants delivered by cesarean section were enrolled and classified into three groups: Group A (exclusively breastfed), Group B (fed standard formula), and Group C (fed probiotic-fortified formula). Stool samples were collected at 6–8 weeks of age and analyzed using 16S rRNA gene sequencing. Microbial diversity indices and taxonomic composition were compared, and the incidence of AD by 6 months was assessed. The incidence of AD by 6 months was 8.3% in Group A, 66.7% in Group B, and 25.0% in Group C ( p = 0.793). Group A showed the highest gut microbial diversity (Shannon, Chao1, and observed amplicon sequence variants), with significantly lower diversity in Group C (adjusted p < 0.017). No significant differences were observed in the Simpson index. Group C exhibited a significantly higher relative abundance of Bifidobacterium compared with Groups A and B (adjusted p < 0.001), while Lactobacillus was most abundant in Group A, with significant differences across all groups (adjusted p < 0.001). The incidence of AD did not significantly differ between Group A and Group C . While early probiotic supplementation via infant formula may support beneficial bacterial colonization in cesarean-delivered infants, its potential role in AD prevention remains to be clarified through further longitudinal studies.

Ahn K. Allergy Asthma Immunol Res. 2026 Jul;18(4):470-473. https://doi.org/10.4168/aair.2026.18.4.470

Jeon YH, et al. Allergy Asthma Immunol Res. 2026 May;18(3):428-439. https://doi.org/10.4168/aair.2026.18.3.428

Chang EY, et al. Allergy Asthma Immunol Res. 2026 Mar;18(2):300-312. https://doi.org/10.4168/aair.2026.18.2.300

Atopic dermatitis (AD) and food allergy (FA) frequently manifest during infancy and share skin barrier dysfunction as a critical early pathogenic event. Recent research has elucidated structural, lipidomic, microbial, and immunologic abnormalities that compromise the skin barrier and contribute to disease onset. Filaggrin gene mutations, altered ceramide profiles, and type 2 cytokine–driven inflammation are among the key factors disrupting epidermal integrity. While AD and FA exhibit overlapping features, including elevated risk in the presence of skin barrier defects, their pathophysiologic pathways are more complicated. This review provides updated evidence on the role of the skin barrier in the pathogenesis of AD and FA. It further highlights the distinction between these conditions and discusses recent findings from birth cohorts and interventional trials. In AD, early emollient application and environmental control show limited but promising preventive effects, particularly in high‐risk infants. In FA, prevention strategies should also address the induction of oral immune tolerance through timely introduction of allergenic foods. Future research should focus on refining predictive biomarkers, validating stepwise interventions, and developing safe, barrier‐based strategies that integrate both prevention and treatment to reduce the burden of AD and FA from early life. image

Background: This study aimed to comprehensively characterize the gut microbiome and identify individual and grouped gut microbes associated with food allergy (FA) using 16S rRNA gene sequencing.Methods: Fecal samples were collected from children with IgE‐mediated FA and from sex‐ and age‐matched controls. The V3–V4 variable regions of the 16S rRNA gene of the gut microbiome were profiled using next‐generation sequencing (Illumina, USA). Bacterial species richness, intracommunity diversity, and intergroup dissimilarity were evaluated. Functional profiles were predicted using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) and the Minimal Set of Pathways (MinPath) algorithm.Results: Fecal samples were collected from children with IgE‐mediated FA (n = 66) and from sex‐ and age‐matched controls (n = 22). Gut microbiome richness (p < 0.0001), intra‐community diversity (p < 0.0001), and inter‐community diversity (p = 0.0004) were higher in the healthy group than in the FA group. Patients with FA were enriched in Blautia, Fusicatenibacter, and Ruminococcus_g5 compared with healthy control individuals (all p < 0.05). Healthy control individuals were significantly enriched in Oscillibacter and Ruminococcus compared with patients with FA (all p < 0.05). Functional pathway analysis identified enrichment in pathways related to endoglucanase in healthy controls and the ATP‐binding cassette (ABC) transport system in FA patients.Conclusions: The gut microbiomes of patients with FA and healthy control individuals had different taxonomic abundances, and the microbiome richness and diversity of the bacterial flora of patients with FA were reduced compared with controls.