Eczema (atopic dermatitis)

Summary

• Atopic dermatitis is a chronic, itching, superficial inflammation of the skin.
• It is often associated with a personal or family history of other allergy-related problems, such as hay fever and asthma.
• The exact cause is not known, but there is strong evidence for a genetic predisposition.
• Itching is a constant feature.
• Emotional stress, temperature or humidity changes, bacterial skin infections, house dust mite, foodstuffs and wool contact may also aggravate the condition.

Definition

This is a chronic, itching, superficial inflammation of the skin, often associated with a personal or family history of related problems such as hay fever, allergic conjunctivitis (‘allergic eyes’) and asthma. Doctors and patients often loosely refer to this condition as ‘eczema’.

Causes

The exact cause is not known. It is felt that interaction of many factors leads to the development of atopic dermatitis. The latest research shows that atopic dermatitis sufferers may have a (genetically) inherited skin barrier defect. This makes the skin dry and strips it of its natural protection from infections and substances that may cause an allergic reaction or irritation. These patients also seem unusually prone to develop inflammation. People who suffer from atopic dermatitis often have high levels of an immune substance called IgE.

Atopic dermatitis is becoming far more common, a trend that is being noticed in many other allergic diseases.

Food allergy may be associated with atopic dermatitis in infants and young children; however there is no evidence of any role of food allergy in teenagers and adults. Your GP or dermatologist can test your child for common food allergies with a simple blood test (Fx5) or using skin prick testing. This is only indicated if there is a poor response to treatment or a very clear history of food-associated flares.

A common sensitivity amongst atopic dermatitis patients is to house dust mite. This may be assessed using skin prick tests. This allergen is however extremely difficult to avoid.

Things that tend to cause atopic dermatitis flares include: staphylococcus growth on the skin, destruction of the skin barrier, exposure to allergens, exposure to irritants (e.g. rough clothing like wool, soaps) and stress.

Symptoms and signs

• The pattern of AD tends to change as a person gets older.
• The condition may start within the first few months of life with red, weeping, crusting lesions on the face, scalp, and the limbs.
• In older children or adults it may be more localised and chronic.
• The redness and thickened skin is most commonly found in the creases in the elbows and knees, the eyelids, neck and wrists. The rash may become more widespread across the rest of the body.
• Itching is a constant feature. The constant itch leads to rubbing and scratching, which in turn leads to more itching. Itching is made worse by the dryness commonly observed in these patients.
• Secondary bacterial infections and swollen glands are common.
• Because people with atopic dermatitis often use drugs, over-the-counter or prescribed, contact dermatitis frequently complicates this condition. There are many substances that irritate the skin and can exacerbate the condition.
• Emotional stress, temperature or humidity changes, bacterial skin infections and wool can also aggravate the condition.

Diagnosis

Diagnosis is usually clinical – which means the doctor examines the skin condition and asks questions to make the diagnosis. It is based on the location of the lesions, how long they have been there and whether there is a family history of allergic disorders. In some cases, if the doctor is not certain of the diagnosis, he/she may take a piece of skin for examination under a microscope (a biopsy). Your doctor may in some cases recommend patch tests, skin prick tests or blood tests for specific allergens. In most cases these are unnecessary.

Treatment

There are several general measures:

• Avoid overheating (turn the air conditioner down etc.).
• Avoid irritants like soaps, bubble baths, etc.
• Avoid wearing rough, irritating fabrics like wool directly on the skin.
• Avoid activities or occupations that may damage the skin e.g. sports involving long periods in the water (this may damage the barrier function of the skin).
• Keep baths short and not too hot.
• Immediately after bathing (within minutes), pat (don't rub) the skin dry and apply appropriate moisturiser (emollient).
• There are a multitude of emollients on the market. Frequently used examples are UEA and CMG. Your pharmacist will prepare this for you. Do not use fragranced body lotions!
• Avoid topical (applied to the skin as creams/ointments) antibiotics and antiseptics (these promote bacterial resistance).
• Fingernails should be kept short to minimise damage when scratching.

Specific treatments:

• Corticosteroid creams or ointments applied to the skin are the most effective drugs. A cream is white in colour and disappears when applied to the skin (best for weeping lesions), while an ointment is fatty and leaves a greasy layer on the skin (best for dry lesions). Prolonged use of high potency corticosteroid creams should be avoided, particularly in infants. Corticosteroids should be used with extreme caution on the face and skin folds. Corticosteroid creams can become ineffective with frequent use. This can be avoided by alternating their use with simple moisturisers for a week or more. The main side effect of topical corticosteroids is thinning (atrophy) of the skin, which may damage its appearance.
• A relatively new group of topical medications has been released on the market, i.e. the calcineurin inhibitors. Pimecrolimus and tacrolimus are available in SA. There have been some safety concerns in the USA with regards to these medications, however most dermatologists feel comfortable using them. They may be a safer alternative in the case of eyelid atopic dermatitis, as there are concerns about using corticosteroid creams near to the eye.
• Children may need a sedative antihistamine at bedtime when the itching is at its worst.
• If the home treatment is not effective, the person may need to be treated in hospital.
• Secondary bacterial infections are treated with antibiotics (these are fairly common due to scratching of the AD).
• Herpes simplex infection (the virus that causes cold sores) can sometimes induce a serious illness with a high temperature, so people with atopic dermatitis should be especially careful about exposure to herpes simplex.
• Oral corticosteroids are used as a last resort.
• Older adults may benefit from psoralen with high intensity ultraviolet light. (Psoralen is a photosensitising drug, meaning it makes you more sensitive to sunlight.)
• In severe cases not responding to conventional treatment, drugs like cyclosporine, azathioprine and methotrexate, mycophenolate mofetil may be used. These are very rarely necessary, and their side effects are severe. It is far better to follow the general advice strictly and apply the creams and ointments diligently.

Course of atopic dermatitis

Atopic dermatitis is a chronic disease. This means that it is usually present for the duration of the patient’s life. A significant proportion of patients (approximately 60%) do grow out of AD, but in those who do not, the disease flares up and calms down in cycles. It is up to the patient to maintain the good condition of the skin by moisturizing and following the other practical advice given above, and by administering rapid treatment to any flares of the condition. In this way, severe flares will be less frequent.

Previously reviewed by Prof H.F. Jordaan

Reviewed by Dr Bianca Tod, MBBCh (Wits), April 2011