BACKGROUND: Several studies have shown that the prevalence of the frequent chronic conditions of atopic dermatitis, asthma, and allergy has increased substantially for reasons not fully understood. Atopic diseases affect quality of life in both children and their family members.

OBJECTIVE: Using national registers, we sought to establish up-to-date incidence rates of atopic dermatitis, asthma, and allergic rhinoconjunctivitis in the Danish and Swedish child populations.

METHODS: Children born in Denmark from 1997 to 2011 or born in Sweden from 2006 to 2010 participated in this cross-national, population-based cohort study. Incidence rates of atopic dermatitis, asthma, and allergic rhinoconjunctivitis in the Danish and Swedish child cohorts were ascertained through disease-specific dispensed prescribed medication, specific hospital contacts, or both.

RESULTS: In both countries the incidence rate of atopic dermatitis was stable during the study periods. The incidence rate of asthma increased until 2006 and stabilized for the rest of the study period in Denmark and increased in Sweden. The incidence rate of allergic rhinoconjunctivitis decreased in both countries.

CONCLUSION: The study revealed similar trends, with stable incidence rates of atopic dermatitis in both Danish and Swedish children, an increase and then stabilization in asthma incidence rates in Denmark and an increase in Sweden, and a decrease in allergic rhinoconjunctivitis incidence rates. At age 5 years, one third of all children were affected with at least one of the conditions of atopic dermatitis, asthma, or allergic rhinoconjunctivitis.