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Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


What is dermatitis? What is eczema?

The terms dermatitis and eczema are often used interchangeably. In some cases the term eczematous dermatitis is used.

Dermatitis / eczema is actually a group of disorders with similar appearance, in which the surface of the skin is dry or blistered. The rash can be acute or chronic or a combination.

Dermatitis affects about one in every five people at some time in their lives.

Acute dermatitis
Acute dermatitis (allergy to adhesive plaster)
Subacute dermatitis
Subacute dermatitis (atopic eczema)
Chronic dermatitis
Chronic dermatitis (atopic eczema)

How is dermatitis diagnosed?

In most cases, dermatitis can be readily diagnosed by its clinical features; an itchy condition in which the skin surface is blistered or dry. However, sometimes a skin biopsy is performed to make or confirm the diagnosis.

The histology of dermatitis (or eczema) includes spongiosis and variable epidermal acanthosis with a superficial perivascular lympho-histiocytic infiltrate. The prominence of one or other feature differs according to how acute the rash is and its underlying cause.

Different forms of eczema/dermatitis are distinguished by age of onset, affected body sites, known causes and other clinical features. Biopsy is not helpful. Combinations can occur, especially in patients with atopy. The table below lists some common forms of dermatitis.

Type of eczema Age of onset Body site Known causes Other features
Atopic dermatitis Before 5 years in 90% Depends on age:
  • Infants: cheeks, extensor limbs
  • Childhood: flexures
  • Adult: face, hands
  • Genetic predisposition
  • Barrier function defects
  • Staphylococcus aureus
  • Associated with asthma, hay fever, food allergy
Seborrhoeic dermatitis First year of life or post-adolesccence
  • Scalp
  • Skin folds of face, ears
  • Sometimes, other flexures
  • Immunological reaction to Malassezia
  • Thin, ill-defined, salmon-pink plaques with yellowish scale
Nummular dermatitis Any age
  • Lower limbs
  • Upper limbs
  • Trunk
  • Skin injury
  • Staphylococcus aureus
  • Round or oval plaques
Eczema craquele Most often elderly
  • Lower legs
  • Xerosis (dry skin)
  • Thyroid deficiency
  • Lymphoma
Venous eczema Middle-aged to elderly
  • Lower legs
  • Venous insufficiency
Signs include:
  • Leg oedema
  • Lipodermatosclerosis
  • Pigmentation
Contact dermatitis Any age Any especially:
  • Hand dermatitis
  • Worst affected areas in direct contact with causative agent.
  • Often unilateral, or if bilateral, asymmetrical, with sharp borders.
  • Patch testing used to detect or confirm allergy
Pompholyx/dyshidrosis Young adults
  • Palms and soles
  • Sweating due to hot environment or stressful event
  • Crops of intensely itchy blisters
Lichen simplex Mainly adults
  • Genitals
  • Nape of neck
  • Forearms
  • Lower legs
Chronic itch:
  • Pre-existing skin disease
  • Neuropathy
  • Patch of thickened skin
  • Often solitary but may be bilateral or widespread
Disseminated secondary eczema Any
  • Distal limbs
  • Trunk
Localised inflammatory reaction
  • Tinea infection
  • Venous eczema
  • Generalised very itchy papules and blisters

What is the treatment of dermatitis?

An important aspect of treatment is to identify and tackle any contributing factors (see above).

Long term control of eczema/dermatitis

Dermatitis is often a long-term problem. Treat dry skin with moisturisers and avoid the use of soap. If the itchy rash returns, use both the moisturiser and the steroid cream or ointment. If it fails to improve within two weeks, see your doctor for further advice.

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Author: A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand. Updated July 2014.

DermNet NZ does not provide an online consultation service.
If you have any concerns with your skin or its treatment, see a dermatologist for advice.