Allergic disorders and immediate skin test reactivity in Finnish adolescents.

We studied the prevalence of allergic disorders in an unselected group of 708 adolescents aged 15-17 years. All subjects were physically examined and interviewed by the authors. The prevalence of past or present asthma was 5.7% in boys and 3.1% in girls. The figures for hay fever were 14% and 8%, and for atopic dermatitis (including allergic urticaria) 25% and 30%, respectively. In 24% of all symptomatic subjects, the condition had not been active during the year preceding the study. The sex difference in the prevalence of hay fever was significant. It is associated with higher immediate skin test reactivity in boys. A progressive increase in the frequency of allergic disorders was observed with increasing number of positive skin reactions in both boys and girls. Respiratory allergy was closely related to a positive skin test: 87% of the asthmatics and 83% of all those with allergic rhinitis exhibited at least one positive skin reaction. For atopic dermatitis the association was less pronounced. Nineteen per cent of the population studied had a positive symptom history and a positive skin test to pollens, animal epithelia or dusts indicating a clinically significant relationship. However, 39% of the 346 subjects with a positive skin test, including some with a large number of positive reactions, were completely asymptomatic.