Development of seasonal allergic rhinitis during the first 7 years of life

Background: Against the background of the controversial discussion about an increase in allergic rhinitis in recent years, intraindividual longitudina l data is lacking for IgE-mediated seasonal allergic rhinitis (SAR), Little is known about the development of SAR in terms of prevalence and incidence rates from birth to school age. Objective: In a prospective birth cohort, we investigated the development o f sensitization and symptoms of SAR. SAR should be defined with high specif icity, and associated risk factors should be determined. Methods: Annual longitudinal data about seasonal allergic symptoms and sens itization was available for 587 children from birth to their seventh birthd ay The definition of SAR was based on a combination of exposure-related sym ptoms and sensitization. Results: Up to 7 years of age, SAR developed in 15% of the children. Incide nce and prevalence of symptoms and sensitization were low during early chil dhood (<2%) and increased steadily with age. Children in which SAR had alre ady developed in the second year all were born in spring or early summer, r esulting in at least two seasons of pollen exposure before manifestation of SAR. Risk factors assessed by multiple logistic regression analysis were m ale sex (odds ratio [OR] = 2.4), atopic mothers (OR = 2.6) and fathers (OR = 3.6) having allergic rhinitis themselves, first-born child (OR = 2.0), ea rly sensitization to food (OR = 3.3), and atopic dermatitis (OR = 2.5), whe reas early wheezing was not associated with SAR. Conclusion: The development of SAR is characterized by a marked increase in prevalence and incidence after the second year of life. Our longitudinal d ata further indicate that in combination with the risk of allergic predispo sition, at least 2 seasons of pollen allergen exposure are needed before al lergic rhinitis becomes clinically manifest.