ABC Health & Wellbeing

Fact File

Eczema and dermatitis

by Peter Lavelle

Eczema and dermatitis are common skin conditions, caused by an allergic reaction or by irritating chemicals. The skin gets red, swollen or blistered, and intensely itchy.

Published 22/11/2007

[Image source: iStockphoto]

• Contact dermatitis
• Atopic dermatitis
• Other types of dermatitis
• More info

Dermatitis is a catch-all term for inflammation of the skin. Eczema is the same thing – the terms are interchangeable (though some people use the term 'eczema' for specific types of dermatitis, such as atopic dermatitis in children).

And though there are different causes of dermatitis, the effect is usually the same: when the skin is inflamed it gets red, swollen or blistered, and intensely itchy.

Contact dermatitis

Contact dermatitis is inflammation of the skin due to contact with a particular substance, either an irritating chemical or an allergen (an allergen is something that causes an allergic reaction).

So-called 'irritant' contact dermatitis is caused by the direct chemical effect of substances such as detergents, solvents, acids, alkalis, oils and skin cleansers. It's common among caterers, cleaners, nurses, builders, hairdressers and mechanics. The hands are often affected.

'Allergic' contact dermatitis occurs when the inflammation isn't caused directly by a chemical, but by an allergic reaction in the skin. Common triggers are creams, gels, lotions, and shampoos; antiseptics in hand creams; fragrances and deodorants; jewellery; hair dyes and bleach. Some people are allergic to metals like nickel and cobalt, and get dermatitis from the backing of watches, jean studs or buckles.

At first, in the acute phase of contact dermatitis, the skin develops a rash; it becomes red and swollen with small, clear, fluid-filled pockets. These break down and weep fluid. The skin is often extremely itchy.

A seven-year-old girl with contact dermatitis on her neck from using antiseptic bath oil in cool compresses. From Moyle M et al, Characteristic adverse skin reactions to antiseptic bath oils. MJA 2007; 186: 652-653. Copyright 2007 The Medical Journal of Australia. Reproduced with permission.

As the condition progresses to the chronic phase, there is less redness and swelling; instead there is thickening of the layers of the skin, often with scaling, fissuring and cracking.

Usually a doctor can recognise contact dermatitis just by looking at it. But sometimes it's hard to tell what has caused the reaction, because the rash often doesn't appear until hours or days after exposure.

The location of the affected skin gives a clue, because the irritant usually only affects those parts of skin it has contacted directly. So if the rash is on the wrist, for example, it may be from the metal on the underside of a wristwatch. A 'streaking' appearance may indicate the person has brushed past a plant to which they're allergic.

If the cause isn't clear but allergic dermatitis is suspected, a doctor might recommend patch testing. This involves placing small amounts of diluted chemicals on discs, which are then placed on a strip of tape called a patch. Several patches are stuck on to the skin and removed after 48 hours, and the skin observed for any allergic reactions. A further reading may be needed two ore three days later.

Whether it's the irritant or allergic type, most cases of contact dermatitis will gradually fade and disappear once exposure stops, though it can take four to six weeks.

In the meantime there are treatments that will reduce the redness and the itching. Emollient creams or ointments and moisturisers soften and add moisture to the skin, improving dryness and scaling. Antihistamines taken by mouth can help relieve the itch. Corticosteroid creams and ointments reduce the inflammation. If the dermatitis is very severe, corticosteroid tablets may need to be given by mouth.

Sometimes, exposure to the chemical or allergen can't be prevented and the person may have no choice but to change jobs.

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Atopic dermatitis

Severe eczema (atopic dermatitis) in a 12-month-old boy. From Katelaris CH and JE Peake, 5: Allergy and the skin: eczema and chronic urticaria. MJA 2006; 185: 517-522. Copyright 2006 The Medical Journal of Australia. Reproduced with permission.

Atopic dermatitis is common in babies and young children. They get a pinkish-red, scaly rash (which is very itchy) on their faces, scalp, behind the ears, over the body and on the arms and legs. The rash can get lumpy, weepy and crusty.

As kids get older, atopic dermatitis tends to clear from the face and is found instead mostly in the elbows, behind the knees, and/or on wrists and hands. If the child scratches the affected area, which they often do because it's so itchy, the skin may become infected.

Atopic dermatitis is more common in children who have other allergies, like asthma and hay fever. It tends to run in families, and it may be triggered by allergens in the environment such as house dust mites, animal dander, grass pollens and moulds. It can flare up and then settle down for no apparent reason.

It usually clears up as the child grows older and is usually gone by adulthood.

Atopic dermatitis can't be cured, but it can be managed. Children with atopic dermatitis have unusually dry, itchy and sensitive skin. They can be helped with:

• bathing in warm (not hot) water
• avoiding soap (it dries the skin)
• using sorbolene cream or some other moisturiser
• wearing soft clothes made of cotton or cotton/polyester mix (not wool or acrylics, which are prickly)
• keeping the child cool, avoiding hot rooms and over-dressing.

The rashes can be helped with a corticosteroid cream or ointment. Antihistamines may control the itching and help the child sleep at night. If the skin becomes infected antibiotics may be needed.

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Other types of dermatitis

Seborrheic dermatitis is a red, itchy, scaly rash on the scalp, face and other areas of the body like the eyebrows, beard, under the breasts, and in the folds of skin in the genital area (these are all areas where there are high numbers of oil glands in the skin).

In adults it affects people aged 20 to 40, men more often than women. Dandruff on the scalp is a mild form of it. In infants when it occurs on the scalp it's known as cradle cap.

Seborrheic dermatitis is thought be caused by a yeast in the skin that breaks down the oil and inflames the skin. It can be hard to treat and it tends to recur, flaring up with stress and with other illnesses. The treatment is to use shampoos containing selenium sulfide or tar products. In severe cases, steroid creams and ointments are used to reduce the inflammation.

Varicose dermatitis. This is a blue/brown discolouration of the skin caused by poor venous circulation, usually because of varicose veins. It's most common in the lower legs and ankles, and is also known as stasis dermatitis.

At first, the skin becomes itchy, reddened and mildly scaly. Over several weeks or months, the skin turns dark brown (cased by staining from blood that's seeped out of veins). The skin may break down and form a painful open sore (ulcer), typically near the ankle. It improves with wearing of compression stockings and treatment of the varicose veins.

Nummular dermatitis. Also known as discoid eczema, this condition usually affects middle-aged people. Small round or oval patches with tiny blisters, scabs, and scales can affect any part of the body, especially the lower leg. They may be itchy but not always. The normal unaffected skin may be dry.

The patches last for weeks or months but clear up, leaving dark (or sometimes pale) marks. The cause isn't known. They're difficult to treat, but skin moisturisers may help. Other treatments include antibiotics taken by mouth, corticosteroid creams and injections, and phototherapy (exposure to ultraviolet light).

Reviewed by Professor Connie Katelaris, Senior Consultant in Clinical Immunology and Allergy at Westmead Hospital and the University of Western Sydney.