High incidence and persistence of allergic sensitization from age 7 to 19 years

Background: Allergic sensitization is the major risk factor for asthma and rhinitis in all ages, however data about the natural history of allergic sensitization is limited. Objective: To evaluate incidence and persistence of allergic sensitization from age 7 to 19 years (y). Methods: The first OLIN pediatric cohort was recruited in 1996 including 2,454 children at age 8 y. The cohort has been followed up annually until 2007. Skin prick tests (SPT) with ten common airborne allergens were performed at age 8, 12 and 19 y, and 2148 (88%), 2060 (84%), and 1868 (76%), respectively, participated. 1515 participated at all three tests (tests (71% of participants at age 8 y). Results: The prevalence of any positive SPT increased significantly by age; 20.6% at age 8 y, 31.1% at age 12 y, and 42.1% at age 19 y. The prevalence was higher among boys at all ages. The sensitization pattern was similar at all ages, sensitization to furred animals and pollen was most common; timothy 27.5% and cat 26.9% at age 19 y. The cumulative incidence of any positive SPT from age 8 to 19 y was 28.3%, while only 10 subjects or 3.1% with a positive SPT at age 8 y had a negative SPT at age 19 y. Of those with any positive SPT at age 8 y, 95% had a positive SPT at age 12 and 19 y. Incidence of specific sensitization was highest for timothy, 22.7%, and dog, 20.8%, followed by birch, 16.7%, and cat 16.2%. The number of positive SPTs at age 19 y was inversely associated with age of onset of allergic sensitization. Conclusion: The high incidence and persistence of allergic sensitization resulted in a consistently increased prevalence by age. Early onset of allergic sensitization was associated with multi-sensitization at age 19 y.