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Background: There is uncertainty about the nature of the relationship between mite allergen exposure during infancy and the expression of allergic diseases in childhood., Objective: We sought to explore the relationships between repeated measurements of mite allergen exposure during the first 5 years of life and clinical allergic disease outcomes at age 5 years., Methods: In a birth cohort of 516 at-risk children, 13 bed dust samples were collected between birth and 5 years of age and analyzed for mite allergen. At age 5 years, the presence of mite atopy was assessed based on skin prick test results, and clinical assessments for asthma, eczema, and wheeze were conducted. The association of allergen exposure with each clinical outcome was examined by means of logistic regression, with adjustments for potential confounders., Results: The lowest and highest mite exposure quintiles, expressed as mean allergen concentration averaged over 0 to 5 years, were associated with a lower prevalence of mite atopy and of asthma compared with intermediate levels of exposure. These relationships, when determined by using average allergen concentration over 0 to 18 months, were weaker., Conclusions: This study demonstrates a nonlinear relationship between mite allergen exposure and clinical outcomes in this generally high mite allergen environment.

Background: Allergen-specific T(H)2-like cytokine responses are considered to be important in sensitization and allergic diseases., Objective: To examine the profile of house dust mite (HDM) stimulated T-cell cytokines and their relationship to allergic disease in children over the period of the first 5 years of life., Methods: Subjects with a family history of asthma who were enrolled antenatally in the Childhood Asthma Prevention Study and had skin prick tests, clinical evaluation for asthma and eczema, and in vitro assessment of lymphocyte cytokine responses to HDM extract performed at ages 18 months (n = 281), 3 years (n = 349), and 5 years (n = 370). IL-13 at 3 and 5 years and IL-5, IL-10, and IFN- gamma at 18 months, 3 years, and 5 years were measured by ELISA., Results: House dust mite-specific cytokine responses increased with age for all cytokines except IFN-gamma. HDM-specific IL-5 responses at 3 years and 5 years were significantly positively related to skin prick test positivity at 5 years. IL-5 responses at 5 years were also significantly related to asthma at 5 years. Other HDM-specific cytokine responses were not related to asthma or eczema at 5 years. Responses were not altered by a HDM avoidance intervention., Conclusion: IL-5 responses to HDM, the dominant local inhalant allergen, are related to the expression of clinical illness at age 5 years., Clinical Implications: The T-cell response to HDM, as reflected in IL-5 production, is acquired over the first years of life and may play a role in the expression of allergic airways disease.

Background: Early life exposures may be important in the development of asthma and allergic disease., Objective: To test house dust mite (HDM) avoidance and dietary fatty acid modification, implemented throughout the first 5 years of life, as interventions to prevent asthma and allergic disease., Methods: We recruited newborns with a family history of asthma antenatally and randomized them, separately, to HDM avoidance or control and to dietary modification or control. At age 5 years, they were assessed for asthma and eczema and had skin prick tests for atopy., Results: Of 616 children randomized, 516 (84%) were evaluated at age 5 years. The HDM avoidance intervention resulted in a 61% reduction in HDM allergen concentrations (microg/g dust) in the child's bed but no difference in the prevalence of asthma, wheeze, or atopy (P > .1). The prevalence of eczema was higher in the active HDM avoidance group (26% vs 19%; P = .06). The ratio of omega-6 to omega-3 fatty acids in plasma was lower in the active diet group (5.8 vs 7.4; P < .0001). However, the prevalence of asthma, wheezing, eczema, or atopy did not differ between the diet groups (P > .1)., Conclusion: Further research is required to establish whether other interventions can be recommended for the prevention of asthma and allergic disease., Clinical Implications: House dust mite avoidance measures and dietary fatty acid modification, as implemented in this trial during infancy and early childhood, did not prevent the onset of asthma, eczema, or atopy in high-risk children.