Disease definition

Atopic eczema (AE) is a non‐infective chronic inflammatory skin disease characterised by an itchy red rash. The terms 'atopic eczema' and 'atopic dermatitis' have been used synonymously. 'Atopy' is defined as "a form of allergy in which there is a hereditary or constitutional tendency to develop hypersensitivity reactions". However up to 40% of children with atopic eczema are not atopic, when defined according to allergy tests such as skin prick tests (Bohme 2001). Others have found that up to two thirds of people with atopic dermatitis are not atopic (Flohr 2004), implying that continued use of the term 'atopic dermatitis' is problematic. A revised nomenclature for allergy (Johansson 2001) has been updated by the World Allergy Organisation (Johansson 2004). The new nomenclature is based on the mechanisms that initiate and mediate allergic reactions. The term 'eczema' is proposed to replace the provisional term 'atopic eczema/ dermatitis syndrome' (AEDS). What is generally known as 'atopic eczema/ dermatitis' is probably not one single disease but rather an aggregation of several diseases with certain characteristics in common. The term 'atopy' can not be used until an IgE sensitisation has been documented by IgE antibodies in the blood of a person or by a positive skin prick test to common environmental allergens such as pollen or house dust mite. The term 'eczema' can therefore be split into 'atopic eczema' and 'non‐atopic eczema'.

Epidemiology and causes

Atopic eczema is the most common inflammatory skin disease of childhood affecting 15 to 20% of children in the UK at any one time (Hoare 2000). Two‐thirds of people with the condition have a family history of atopic eczema, asthma or hay fever. The cumulative prevalence of atopic dermatitis varies from 20% in Northern Europe and the USA to 5% in the south‐eastern Mediterranean (Thestrup 2002). Prevalence data for the symptoms of atopic eczema were collected in the global ISAAC study (International Study of Asthma and Allergies in Childhood). The results of this study suggest that atopic eczema is a worldwide problem affecting 5 to 20% of children (Williams 1999). Only 2% of children under the age of five years have severe disease and 84% have mild disease (Emerson 1998). Around 2% of adults have atopic eczema and many of these have a more chronic and severe form (Charman 2002). Atopic eczema is often associated with other atopic diseases (Beck 2000) e.g. asthma and rhinitis and sufferers often have a family history of the condition. The incidence of common allergic disease has increased in the past 30 years (Fendrick 2001). The increase in prevalence of atopic disease in the past three decades appears to be a real phenomenon and has been observed in countries as far apart as Japan, USA, Finland and Africa (Williams 1992).

The cause of eczema is not well understood and probably is due to a combination of genetic and environmental factors (Cookson 2002). In recent years research has pointed to the possible role of environmental agents such as house dust mite (Van Bever 2002), pollution (Polosa 2001), and prenatal or early exposure to infections (Kalliomaki 2002).

Clinical features

Atopic eczema may be acute (short and severe) with redness, scaling, oozing and vesicles, or it may be chronic (long‐term) with skin thickening, altered pigmentation and exaggerated surface markings. The condition affects mainly the creases of the elbows and knees, and the face and neck, although it can affect any part of the body. The severity of eczema is variable, ranging from localised mild scaling to generalised involvement of the whole body, with redness, oozing and secondary infection. Itching is the predominant symptom which can induce a vicious cycle of scratching, leading to skin damage which in turn leads to more itching ‐ the so called "itch scratch itch" cycle. There is a tendency to a dry sensitive skin, even in those who have 'grown out' of the disease. This is thought to be due to a defect in the lipid barrier of the epidermis. In adulthood, the skin (especially of the hands) may be prone to inflammation in the presence of environmental irritants such as soaps (Archer 2000).

Natural history

Atopic eczema usually starts within the first six months of life, and by one year, 60% of those likely to develop it will have done so. Remission occurs by the age of 15 years in 60 to 70% of cases, although some relapse later. In the more severely affected child, development and puberty may be delayed (Baum 2002).

Impact

Atopic eczema varies in severity, often from one hour to the next. Severity can be measured in a number of ways. A systematic review of named outcome scales for atopic eczema found that of the 13 named scales in current use, only one (Severity Scoring of Atopic Dermatitis, SCORAD) had been fully tested for validity, repeatability and responsiveness (Charman a 2000). The itching and scratching can adversely affect quality of life through chronic sleep disturbance. This may have an impact on family life. The disease can be associated with complications such as bacterial and viral infections (McHenry 1995). The unsightly appearance of the skin and the need to apply greasy ointments can limit a child's inclination to participate in social and sporting activities and thus affect their confidence. Adults with atopic eczema often have low self‐esteem and relationships can be difficult to initiate and sustain. Everyday tasks such as housework, gardening, childcare and food preparation present problems when the skin on the hands is cracked. Promotion at work may be blocked for people who do not 'look good'.

There is a substantial economic cost not only to the family of the person with atopic eczema (Kemp 2003) but also to the health services of the country as a whole (Herd 1996; Verboom 2002). Direct costs to the family are encountered when purchasing treatments, special clothing and bedding; indirect costs are experienced from lost working days when parents are looking after a sick child. The wider economic implications lie in the costs of health professionals, the lost opportunities of parents of sick children who do not have the option of seeking employment and the child who, as a result of missing schooling, has limited employment prospects (Su 1997).

Diet and atopic eczema

Many people with atopic eczema are reluctant to use the most commonly recommended treatments because they fear the long‐term health effects (Charman 2000). As a result, many turn to dietary supplementation as a possible treatment approach, often with the belief that some essential ingredient is 'missing' in the diet of the affected individual. A number of dietary supplements have been tried, and these can be broadly classified into: