Patterns of sensitization to food and aeroallergens in the first 3 years of life

Background: There is a paucity of longitudinal studies of allergen sensitization in childhood. Objective: To investigate the pattern of sensitization in early childhood. Methods: A nested cohort of children (n = 543) were followed up from birth and given a skin prick test (SPT) at 1, 2, and 3 years of age. A detailed clinical history was obtained. Results: The prevalences of sensitization to aeroallergens were 1.3%,6.4%, and 10.7% at 1, 2, and 3 years of age. The figures for food allergens were 2.8 %, 3.9 %, and 3.7 %. There was a statistically significant increase in the prevalence of sensitization to >= 1 allergen between years 1 and 2 (P <.001) and years 2 and 3 (P =.032). Among those with a positive SPTat 1 year, 29% tested positive to additional allergens at 2 years (P =.0054). Sensitization to milk or egg at 1 year was a predictor for increased sensitization to peanut at 3 years (odds ratio, 34.8; P <.0001). Sensitization to egg at 1 year was associated with increased sensitization to aeroallergens at 3 years (odds ratios, house dust mite, 27.1, P <.001; cat, 8.9, P <.01; grass, 11.8, P =.005). For peanut and cat allergens, wheal size increases with the age of the child (P =.009 and P =.017, respectively). Conclusion: Sensitization to allergens as demonstrated by positive SPT tends to increase with age, and this change can be detected in the first 3 years of life. Clinical implications: The high predictive value for early sensitization and a linear increase in SPT reactivity provide an opportunity for early intervention.