Background: Up to two-thirds of children with atopic dermatitis have IgE-mediated allergic reactions and a Th2 immune reactivity pattern with low production of interferon gamma and high production of interleukin 4 after allergen stimulation of T lymphocytes. Insulin-dependent diabetes mellitus (IDDM) seems to be associated with a Th1 immune reactivity pattern. We therefore postulated that these diseases may be inversely associated.
Methods: We designed a case-control study including 920 children with IDDM, registered in the Danish Registry for Childhood Diabetes, and a sample of 9732 non-diabetic children registered in the Danish Medical Birth Registry. The children were aged 3-15 years. Information on atopic dermatitis was obtained by questionnaires.
Findings: The cumulative incidence of atopic dermatitis up to age 15 years was 13.1% among children with IDDM and 19.8% in non-diabetic children (p<0.0001). Among children who developed IDDM, the incidence of atopic dermatitis was significantly lower than in the controls before onset of IDDM (73 cases in 5314 person-months vs 1375 in 57432 person-months; odds ratio 0.49 [0.39-0.63]). After onset of IDDM, diabetic and non-diabetic groups did not differ in incidence of atopic dermatitis (1.36 [0.89-2.07]).
Interpretation: Our findings may be explained by different acquired or inherited reactivity patterns associated with atopic dermatitis (Th2) and IDDM (Th1). The results do not allow us to find out whether early development of atopic dermatitis reduces the risk of IDDM, or a propensity for IDDM reduces the risk of early-onset atopic dermatitis.