The problem of atopic eczema: aetiological clues from the environment and lifestyles.

Atopic eczema is the most common inflammatory skin disease in children, affecting around 10% of children in the developed world. It can be a distressing condition, influencing children's well-being, personal and educational development, and family life, and it has huge economic implications for health services and individual budgets. Like other atopic diseases such as asthma and hay fever, the prevalence of atopic eczema has increased substantially over the last 30 years, for reasons largely unknown. Although a genetic predisposition to the disease has been implicated, evidence from a range of sources suggests that environmental factors play a crucial role in the disease expression. This paper reviews the epidemiology of atopic eczema, with particular attention to potential environmental aetiological factors and draws evidence from studies in the UK and internationally. First, atopic eczema has been found to vary socially and to be more prevalent in the UK among social class I and II families than among other socio-economic groups. Second, it has been suggested that cross infection from other siblings in large families may have a protective role in atopic disease expression. Third, it has been proposed that an increased risk of atopic eczema may result from decreases in helminthic infestation. Fourth, studies of migrant groups have shown large increases in disease prevalence compared with migrants' country of origin, suggesting clues as to the importance of socio-economic and environmental changes such as those associated with industrialization. Finally, a distinct and consistent geographical pattern of eczema has been observed in the UK which cannot be explained by social class distribution. The various types of study have attempted to identify reasons for differences in prevalence but, to date, no definitive causation has been identified. In some cases, specific risk factors have been suggested and include house dust mites, dietary allergens and irritants. It is argued here that the aetiology is unlikely to be simple or uni-causal and that an understanding of the relationships between the disease and behaviour, lifestyle, home and external environmental factors is crucial. This paper reports the preliminary stages of an interdisciplinary research project involving dermatologists, epidemiologists and health geographers, and calls for investigation into associations between atopic eczema and possible environmental and lifestyle factors. These include behavioural factors, microenvironment factors and macroenvironments.