Occurrence of atopic diseases in three generations.

The incidence of asthma, hay fever and atopic dermatitis was assessed in three generations in 2820 families by a questionnaire. 35% of the families were atopic when the histories of parents and grandparents were included. 64% of atopic children had atopy in probands and the corresponding figure for non-atopic individuals was 31%. The highest prevalence of atopy was found in the parents' generation (13.5%) but it did not differ significantly from that of children (10.8%) when compared with grandparents (7.6%). The results suggested an increasing prevalence of children's atopic dermatitis in Finland since the 1950s. The influence of heredity was apparent. Few geographical differences were observed.