Eczema is one of the commonest rashes affecting more than 10% of the population. It is a medical term used to define a specific type of skin inflammation (spongiosis). It is often but not always itchy though the presentation can vary from simply dry, rough patches to red spots and patches to blistering to painful cracks.
There are different types of eczema:
1. Atopic eczema
This often starts in infancy though it can present at any age. People with atopic eczema has genetic predisposition of atopy (hyper-reactive immune system to environmental stimuli). Asthma and allergic rhinitis are often present. They often have dry skin.
2. Seborrhoiec eczema
This is seen during first six month of life and after puberty. It is eczema presents on oily skin (scalp, face, chest, back, genitalia). It often presents as dry, peeling skin and often not as itchy as other form of eczema.
3. Contact eczema
This is eczema resulted from skin irritation or allergic reaction to a substance. Hand eczema seen in a housewife is often due to irritation by prolonged water and detergent contact. A person with nickel allergy may present as eczema patches on neck due to necklace containing nickel or on earlobe due to nickel containing earring.
4. Asteatotic eczema
This is eczema due to excessive dryness of skin. This is often seen in elderly, or people who have been overseas and exposed to climates with low humidity.
5. Endogenous eczema
This is a term used to describe eczema without any identifiable external factors (presumably from an unknown internal factor).
This is not entirely understood. There is likely an underlying genetic predisposition and an environmental trigger. Researchers are only beginning to identify some of these eczema genes and while the environmental factor is clear as in contact eczema, it is often not known in most cases.
Many external factors while not causing eczema can aggravate it. Such factors include dry climate, heat & sweating, dusty environment, food allergy, viral infection, vaccination, stress.
The diagnosis of eczema is often based on history and appearance of the rashes or clinical features of the rashes only.
There is no blood test which can diagnose eczema. Total IgE or eosinophil count is often raised but it is not diagnostic of eczema. Blood test (RAST test) may also be done in selected cases to evaluate for the role of allergy.
Skin prick tests and patch tests may be done in some cases to evaluate for the role of allergy in aggravating the eczema.
Occasionally, a skin biopsy is done in clinically difficult cases.
While there is no cure for eczema, it can be treated or controlled so well that the patients can have long term remission with occasional flare only. Treatment aims to control the skin inflammation and to improve the skin barrier function.
Topical moisturiser not only hydrates the skin but improve the skin barrier function. It is particularly useful in prevention of eczema flare and thus reducing the needs for the topical corticosteroid.
Topical cortico-steroid is a very effective treatment for eczema, Used judiciously, it is very safe with negligible absorption into the body and negligible side effect on the skin itself. It comes in various strength and preparation for skin on different part of body, eczema of different severity and ease of use.
Topical calcineurine Inhibitor (tacrolimus and pimecrolimus) is a good supplementary treatment to topical cortico-steroid. It is particularly useful for eczema on face and around the eyes, and eczema needing a long period of treatment.
Oral antihistamine is often dispensed as anti-itch. Sedative anti-histamines work better than non-sedative anti-histamines. It is particularly useful if there is co-existing urticaria with the eczema. It may be given long term in the more difficult eczema.
Oral antibiotic is useful in eczema with secondary bacteria infection.
Phototherapy is a reasonable option in patients needing more intensive regimen of treatment. The need for frequent visit to a phototherapy centre (1-3 times a week) and the relatively slow onset of action make it less attractive.
Cortico-steroids, cyclosporine, azathioprine taken orally are very effective treatment but only used in the most severe cases of eczema due to potential risk of side effects.