A half of schoolchildren with 'ISAAC eczema' are ill with allergic contact dermatitis

Background Similarity in clinical symptoms between atopic eczema (AE) and allergic contact dermatitis (ACD) may lead to misdiagnoses in both clinical practice and epidemiological studies. As patch testing for contact allergy does not seem popular among paediatric allergists, the resulting bias leads mainly to under diagnosing of ACD and over diagnosing of AE in children and adolescents. Objectives To assess the frequency of AE and ACD among children and adolescents who answered affirmatively the eczema module of ISAAC questionnaire. Methods Of 9320 schoolchildren involved in an allergy screening programme, 143 consecutive participants were recruited for the present study. The inclusion criterion was affirmative answers to questions from the eczema module of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. The children were examined by two allergists: a paediatrician and a dermatologist, and the children underwent patch testing. Results We diagnosed AE in 46 (55.4%) children and 18 (30.0%) adolescents, whereas 32 (38.6%) children and 31 (51.7%) adolescents were diagnosed with ACD, with a considerable overlap of both diseases. Nine of 46 (19.6%) children and 13 of 25 (52.0%) adolescents with affirmative answers to the question about flexural eczema were diagnosed with ACD, while lacking features sufficient for the diagnosis of AE according to Hanifin and Rajka. Based on the indices from the whole population tested (9320 pupils), a rough estimate of the general ACD prevalence was 5.8% for adolescents, and 8.5% for children, which is close to the figure of 7.2% observed previously in Danish schoolchildren. Conclusions Our data demonstrate that ‘ISAAC eczema’ is an epidemiological entity that embraces comparable portions of cases of atopic eczema and allergic contact dermatitis, and possibly also other less frequent pruritic dermatoses. Each case of chronic recurrent dermatitis in children requires differential diagnosis aimed at allergic contact dermatitis and inflammatory dermatoses other than atopic eczema, even when predominantly localized in flexural areas.