BACKGROUND: Allergic reactions to airborne allergens may have important consequences for affected individuals and are believed to be unstable through life, although evidence from longitudinal studies is limited.

OBJECTIVE: To assess changes in skin prick reactivity during 20 years in a random population sample of children and adolescents in relation to symptoms of rhinitis.

METHODS: A total of 983 individuals, aged 7 to 17 years, were randomly selected in 1986 and invited to 4 examinations during a 20-year period. During each examination, a skin prick test was performed using common local aeroallergens (ie, birch, grass, mugwort, horse, dog, cat, house dust mite [Dermatophagoides pteronyssinus and Dermatophagoides farinae] and 2 molds [Alternaria iridis and Cladosporium herbarum]).

RESULTS: The prevalence of allergy to any tested allergen peaked at the ages of 13 to 23 years. Rates of sensitization were variable. In the group of individuals tested more than once (n = 592), 16% developed sensitization during the study period and 9% became desensitized. In the group of individuals tested at all 4 examinations (n = 148), 34% developed sensitization and 22% became desensitized. In the group who developed sensitization, 55% had rhinitis, 17% had asthma, and 70% had eczema. In the group who became desensitized, 30% had rhinitis, 10% had asthma, and 50% had eczema.

CONCLUSION: This 20-year prospective study found that sensitization is common, but its prevalence in individuals is also variable over time. Furthermore, through puberty and early adulthood a large number of individuals develop sensitization and a smaller number become desensitized. In addition, we found that symptoms of rhinitis rarely preceded sensitization.