What causes eczema?

Although the exact cause of eczema is unknown, it appears to be linked to the following internal and external factors:

Internal factors

  • A family history of eczema, asthma or hay fever (the strongest predictor) - if both parents have eczema, there is an 80 per cent chance that their children will too
  • Particular food and alcohol (dairy and wheat products, citrus fruits, eggs, nuts, seafood, chemical food additives, preservatives and colourings)
  • Stress

External factors

  • Irritants - tobacco smoke, chemicals, weather (hot and humid or cold and dry conditions) and air conditioning or overheating
  • Allergens - house dust mites, moulds, grasses, plant pollens, foods, pets and clothing, soaps, shampoos and washing powders, cosmetics and toiletries.


The word ‘eczema’ comes from Greek words that mean ‘to boil over’. ‘Dermatitis’ comes from the Greek word for skin – and both terms refer to exactly the same skin condition. Eczema or atopic eczema is a skin condition characterized by chronic inflammation and frequent relapses. There are itchy red rashes over the affected areas that usually involve skin creases such as the folds of the elbows or behind the knees.

Atopic eczema is common and the prevalence of the condition is on the rise. Eczema affects 15-20% of school children and 2-10% of adults. Most of the cases (nearly 80%) are in children less than 5 years of age. Children with a parent who suffers from the condition are more likely to get the condition.

Eczema is divided into a small number of subgroups based largely on the factors that may be most important in causing eczema in any one individual. But it's important to recognise that the symptoms and appearance of the skin in all these types can be exactly the same. Also, the classification system is far from perfect as it is often difficult or impossible to accurately say what causes eczema to occur in any one person. The lines of treatment of the different types of eczema are also similar.

The main differences are to do with the particular factors causing an individual’s eczema. Therefore, if it's thought to be mainly due to exposure to an irritant substance at work – removal or protection from this irritant will be an important part of managing that person’s eczema, compared to someone else with no such history of exposure.

Main groups

  • Atopic: the ‘allergic’ type often seen in people who also have hay fever or asthma.
  • Allergic contact: due to skin contact to a substance to which the individual is sensitive. The same substance does not cause eczema in a person who is not sensitive to it.
  • Irritant contact: due to skin contact with irritating chemicals, powders, cleaning agents, etc. Contact with such a substance is likely to cause eczema in any person, although a degree of individual variation still exists.
  • Discoid: appears as discrete islands of eczema on a background of normal skin.
  • Seborrhoeic: in infants appears in the nappy area and the scalp. In adults, also appears on the scalp and in the skin creases between the nose and sides of the mouth. It can be caused by an increased sensitivity to yeast living on the skin.
  • Others: a miscellaneous group including eczema of the legs caused by varicose veins and pompholyx – an intensely itchy form located on the hands and composed of small or (sometimes) large blisters.