Relevance of Low Specific IgE Levels to Egg, Milk and Peanut in Infancy

Abstract

To evaluate the clinical importance of low specific immunoglobulin E (IgE) to hen’s egg, cow’s milk, and peanut at 6 months in relation to doctor’s diagnosis of allergy-related disease at 5 years of age.Families in Sweden were recruited between 2004 and 2011 (ALADDIN prospective birth cohort). This study included 372 children, all of whom contributed a blood sample at 6 months and at 1, 2, and/or 5 years of age. Fifty percent were girls, 17% were born via cesarean delivery, and 26% were breastfed exclusively for 6 months. At 6 months, 11% had a doctor’s diagnosis of asthma, 12% had a diagnosis of eczema, 3% had a diagnosis of allergic rhinoconjunctivitis, and 8% had a diagnosis of food allergy.Questionnaires regarding lifestyle, background, diet, and health were completed at enrollment, 2 and 6 months, and 1, 2, and 5 years of age. Serum IgE to specific foods and aeroallergens was measured in children at 6 months and 1, 2, and 5 years. For the statistical analysis, 3 categories were designated: nonsensitized (<0.1 kU/L), low sensitized (0.1–0.34 kU/L), and sensitized (≥0.35 kU/L); proportion with allergy-related disease was assessed.For egg and milk, having specific IgE in the interval of 0.1 to 0.34 kU/L at 6 months was significantly associated with being sensitized (≥0.35 kU/L) to that specific allergen at 1 year (P = .01 and <.01, respectively) and to aeroallergens at 5 years (P = <.01 and .01), compared with nonsensitized children. Being sensitized (≥0.35 kU/L) to egg or milk at 6 months was significantly associated with sensitization to the food at 1 and 2 years of age and to any food allergen, but it was not associated with aeroallergen sensitization at 5 years as compared with those with low sensitization (P = .69). Approximately 50% of children with low sensitization to milk or egg at 6 months had IgE that declined to nonsensitized levels at 2 years of age. For peanut, low sensitization at 6 months was only significantly associated with being sensitized to aeroallergens at 5 years of age (P = .04). Low-level sensitization to egg was associated with higher rates of eczema (P < .01).Specific IgE to milk, egg, and peanut in the range of 0.1 to 0.34 kU/L at 6 months appeared to decrease over time. However, low-level sensitization at 6 months appeared to increase the likelihood of sensitization to aeroallergens at 5 years. Compared with those who were nonsensitized at 6 months, children with low sensitization to milk or egg had higher rates of sensitization to that allergen at 1 year of age. Having low sensitization to egg at 6 months was associated with the development of eczema.Researchers in this study evaluated whether specific IgE at 6 months was associated with further IgE sensitization and allergy-related diagnosis. The strengths of the study include that it was population based and managed children over the course of 5 years. The study does not provide any data about the development of clinical food allergy. This study suggests that children with low sensitization at 6 months can be counseled that ∼50% had undetectable IgE to the relevant allergen at 2 years, but the low sensitization could suggest a higher risk of future aeroallergen sensitization as well as potentially eczema for those with egg-specific IgE.