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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 >or=1 allergen between years 1 and 2 (P < .001) and years 2 and 3 (P = .032). Among those with a positive SPT at 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.

Background There are very few population-based studies investigating the incidence of food hypersensitivity during the first year of life. Objective To determine the incidence of parentally reported food hypersensitivity and objectively diagnosed food hypersensitivity during the first year of life. Methods A birth cohort was recruited (n = 969). At 3, 6, 9, and 12 months, information regarding feeding practices and reported symptoms of atopy were obtained. At 1 year, infants underwent a medical examination and skin prick testing to a battery of allergens. Symptomatic infants underwent food challenges. Results Adverse reactions to foods were reported by 132 (14.2%) parents at 3, 83 (9.1%) at 6, 49 (5.5%) at 9, and 65 (7.2%) at 12 months. Of the subjects, 1.0% (8/763) were sensitized to aeroallergens and 2.2% (17/763) to food allergens. Between 6 and 9 months and 9 and 12 months, 1.4% (14/969) and 2.8% (27/969) infants were diagnosed with food hypersensitivity on the basis of open food challenges and 0.9% (9/969) and 2.5% (24/969) on the basis of double-blind, placebo-controlled food challenges. Cumulative incidence of food hypersensitivity by 12 months was 4% (39/969; 95% CI, 2.9% to 5.5%) on the basis of open food challenges and 3.2% (31/969; 95% CI, 2.2% to 4.5%) on the basis of double-blind, placebo-controlled food challenges. Conclusion Between 2.2% and 5.5% of infants have food hypersensitivity in the first year of life. The rate of parental perception of food hypersensitivity is higher than the prevalence of atopic sensitization to main food allergens or objectively assessed food hypersensitivity. Clinical implications In the first year of life, the rate of parentally perceived food hypersensitivity is considerably higher than objectively assessed food hypersensitivity.

RATIONALE: This study provides information on changes in sensitisation rates in children on the Isle of Wight. METHODS: Three cohorts of children were recruited and underwent skin prick tests to a predefined panel of allergens (milk, egg, peanut, cod, house dust mite, cat and grass) by standard methodology. Wheat sensitisation was not analysed for Groups C and D due to different solutions used. Group A: Children born 1989, tested at four years (1993). Group B: Children born 2001/02, tested at three years (2004/05). Group C: Children born 1989, tested at ten years (1999). Group D: Children born in 1991/92, tested at 11 years (2002). RESULTS: Sensitisation to predefined food allergens increased significantly from 1.8% in 1993 (Group A) to 4.2% in 2004 (Group B) (p = 0.008). When wheat-grass cross-reactors were excluded, increase was no longer significant (p = 0.31). In contrast sensitisation to aeroallergens showed a significant decrease from 14.8% to 10.9% (p = 0.006). Notable decreases were seen in HDM (p = 0.006), and grass, (p = 0.013). A significant rise, from 2.2% in 1999 (Group C) to 4.6% in 2002 (Group D), was observed in sensitisation to food allergens (p = 0.008). Sensitivity to peanut (p = 0.1023) and grass (p = 0.0115) rose significantly. CONCLUSION: Prevalence of sensitivity to both food and aeroallergens was seen to be greater amongst older children than younger children. Amongst younger children we found a significant reduction in prevalence of sensitisation to aeroallergens. Amongst older children we found a significant increase in prevalence of sensitisation to food allergens.