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Description and causes of eczema

Eczema, also commonly known as dermatitis, is the broad clinical name given to a host of dermatological (skin) inflammatory conditions. There are at least 19 different types of eczema, many of which are unrelated to each other in terms of the underlying cause.

Factors which may trigger eczema can be classified into two broad categories:

  1. Those originating external to the body (exogenous factors). What is known as "Hand Eczema" is an example of this. In this form of eczema, the inflammatory reaction results from the use of skin irritants such as detergents.

  2. Those originating from within the body (endogenous factors). "Stasis Eczema" is an example of endogenously triggered eczema and results from swelling in the legs associated, for example, with varicose veins.

Multiple trigger factors, sometimes of both external and internal type, may act in combination to cause the disease. The underlying cause of individual cases of eczema, therefore, is often much more complicated than the above classification system suggests.

While the true clinical presentation of the disease is very broad, what most people think of as "eczema" is probably that form which is very common in babies and infants. This is known as "Atopic Eczema" and is common in infants and children who suffer from the respiratory allergic conditions asthma and hay-fever. Because atopic eczema is associated with allergic conditions, it is often assumed that this type of eczema is itself the result of an allergic reaction.

While this may be the case in many instances, where allergens (allergy causing substances) such as house dust mites, pollen and certain foods (for example, milk, eggs and nuts) have been implicated, other factors such as infection and climate have also been suggested as possible causes. A genetic susceptibility to allergy, as well as environmental factors, therefore, are likely to be important in the development of atopic eczema.


Eczema, in general terms, is characterised by itching, redness and scaling of the skin. To some degree or another, these are symptoms of all types of eczema.

In the case of atopic eczema, the areas most commonly affected are the "hot and sweaty" skin fold areas of the body, such as behind the knees and in front of the elbows. Itching may occur on and off all through the day, but tends to be worse in the evening and at night. As a result, disruption of sleep is also quite common.


Eczema of all types account for approximately 30% of all dermatological conditions, with a prevalence in the general population of around 20 cases per 1000 individuals.

It is difficult to determine the relative prevalence of the different types of eczema because of inconsistencies in the way they are named and classified. Generally, however, eczemas of the exogenous type tend to outnumber those of endogenous cause by approximately 2:1.

Atopic eczema affects approximately 10-20% of infants and children in Western countries and approximately 2-3% of adults. The majority of children, therefore, "grow out of" eczema before they reach adulthood. Statistics suggest that 60% of children with eczema are also likely to have asthma. The prevalence of atopic asthma has been increasing in children over the past 30 years and is more common in urban compared with rural areas. The reason for this is not fully understood, but may relate to indoor climates promoting allergens, changes in diet or reductions in breast feeding.


It is important to be able to distinguish eczema from other causes of skin reactions (fungal infections, for example), because the treatment of each will be quite different. Clinical examination of affected areas, together with a possible family history of eczema and other allergic<

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