Environmental food allergen levels in the homes of 3–4-month-old infants: findings from the second phase Chiba study of mother and child health (2nd C-MACH)

Pediatric food allergy is a growing health concern, with hen's egg, cow's milk, and wheat being the most common allergens in Japan. The dual allergen exposure hypothesis proposes that early oral intake induces immune tolerance but that cutaneous exposure may promote sensitization. However, little is known about environmental exposure to food allergens before the introduction of complementary foods. This study investigated the presence and concentration of food allergens in the home environments of 3- to 4-month-old infants who had not yet started complementary feeding. Dust samples were collected from 26 households participating in the C-MACH birth cohort study. Allergen concentrations for hen's egg, cow's milk, wheat, peanut, walnut, and house dust mites (Der f 1, Der p 1) were measured using ELISA. Statistical analyses were performed using the Kruskal-Wallis and Steel-Dwass tests. Hen's egg, cow's milk, wheat, and Der f 1 were detected in all samples. Peanut, Der p 1, and walnut occurred in 88%, 81%, and 35% of samples, respectively. Hen's egg, cow's milk, wheat, and peanut allergens were present at significantly higher concentrations than house dust mite allergens. These findings suggest that environmental exposure to food allergens begins prior to oral intake and may contribute to sensitization via the skin. This underscores the importance of considering both dietary and environmental sources in strategies for food allergy prevention. The study provides preliminary evidence of allergen exposure in early infancy and highlights the need for longitudinal research to examine its role in the development of allergic diseases.