Chiba University study finds infants may be exposed to multiple food and mite allergens through bedding before starting solid foods

A research group led by Associate Professor Norimichi Suzuki and Project Lecturer Keiichi Shimatani of Chiba University’s Center for Preventive Medical Sciences investigated the levels of food and mite allergens present in the home environments of infants aged 3 to 4 months, before they had started solid foods. The study focused especially on bedding, which infants touch for long periods, and examined the presence and concentration of allergens. The findings indicate that even before starting solid foods, infants may already be exposed to multiple allergens through their bedding. The study was published online in Scientific Reports on March 19, 2026. DOI: 10.1038/s41598-026-45145-5. Background: Food allergy in children is a major health concern. In recent years, the “dual-allergen exposure hypothesis” has attracted attention. This theory proposes that oral intake of food helps the immune system develop tolerance, while exposure through the skin may promote allergic sensitization. Previous reports have suggested that introducing small amounts of egg early in life can reduce the risk of egg allergy. However, little was known about how much allergen exposure infants experience at home before they begin solid foods. For 3- to 4-month-old infants who cannot yet move independently, bedding and floors are areas that remain in prolonged contact with the skin and may create conditions for allergic sensitization. In addition, a previous JECS pilot study found egg antigen at higher concentrations than mite antigen in the bedding of 3-year-old children. In this study, the researchers measured levels of mite allergens Der f1 / Der p1, egg, cow’s milk, wheat, peanut, and walnut in the bedding of 3- to 4-month-old infants from 26 households participating in the 2nd C-MACH birth cohort study, using the ELISA method. Findings: Egg, cow’s milk, wheat, and mite allergen Der f1 were detected in every household. Peanut was detected in 88% of households, mite allergen Der p1 in 81%, and walnut in 35%. Concentrations of some food allergens were clearly higher than those of mite allergens. Cow’s milk showed the highest median concentration at 330 μg/g dust. Egg measured 73 μg/g dust and wheat 110 μg/g dust, while mite allergens were lower, with Der f1 at 3.5 μg/g dust and Der p1 at 0.62 μg/g dust. These results suggest that infants may be exposed to food allergens through their home environment before they consume those foods orally. Outlook: This study quantitatively shows that infants before the start of solid foods are already exposed to food allergens in their home environment. Although preliminary, the findings suggest that infants may contact allergens through the skin before eating them. Further long-term follow-up studies are needed to clarify causal links between infant eczema, environmental allergen exposure, IgE sensitization, and the development of allergic disease. Terminology: The dual-allergen exposure hypothesis proposes that food allergy develops through two pathways: sensitization through the skin and immune tolerance through oral intake. Der f1 and Der p1 are major mite allergens produced by Dermatophagoides farinae and Dermatophagoides pteronyssinus, respectively. ELISA is a method that uses specific antigen-antibody reactions to measure target substances, such as allergens, through color changes. IgE sensitization refers to the state in which IgE antibodies against a specific allergen are produced and bind to mast cells or basophils, creating the potential for allergic reactions upon re-exposure to the same allergen. Funding: The study was supported by JSPS KAKENHI grants B, JST OPERA, and partial support from Duskin Co., Ltd. The funders were not involved in data interpretation.