Atopic Eczema

Atopic eczema (also called atopic dermatitis) is a group of diseases involving inflammation of the skin with intense itching, reddening, dryness, blistering and scaling. Since not all cases are linked to allergy, the preferred term is "the Atopic Eczema/Dermatitis Syndrome" (AEDS). AEDS is not contagious - it cannot be transmitted by, or to, another person. It is a condition that may continue to occur, with varying degrees of severity, over a number of years.

Epidemiology and Classification

With a prevalence of 2-5% (in children and young adults approximately 10%), AEDS is one of the most commonly seen skin disorders. Atopy, the propensity of an individual to develop allergic reactions, is inherited, and atopy is a common finding in people with AEDS. The atopic (IgE-mediated) diseases, AEDS, allergic asthma and allergic nasal and eye symptoms are genetically linked within families.

In some people with AEDS, true allergic reactions, those involving the IgE antibody, are clearly responsible for the development of the disease. There are, however, also many individuals in whom non-specific factors, such as skin irritants or psychological influences, appear to be important. AEDS consists of at least two different disorders. Patients belonging to the IgE-associated subgroup of AEDS will get worsening of their eczema upon contact with classical allergens, e.g., animal hairs. The other subgroups of AEDS are less well understood, but they are believed to result from internal mechanisms.

Symptoms and Signs, Differential Diagnosis

AEDS often begins with "cradle cap" in babies, after the first 3 months of life. As the baby becomes a toddler, the disease spreads to the face, outer elbows and knees, and the skin becomes oozing and crusting. Later on, eczema develops on the neck, hands, the inner elbows, and behind the knees. The skin becomes dry and scaly as a result of scratching and rubbing. In adults, this may also result in weeping, itchy lumps and patches, the "prurigo form" of AEDS. New flare-ups of AEDS often start without obvious symptom, except for increased itching, which is followed by raised red lumps. These features can also occur in other skin disorders, and so to confirm a diagnosis the doctor will look for four of the following symptoms:

• Areas of skin showing the typical appearance of eczema
• Early onset of symptoms of eczema
• Typical location of the affected areas, bearing in mind the patient's age
• Itching
• Personal or family history of IgE-mediated allergic diseases - eczema, hay fever, asthma
• Evidence of IgE-mediated reactions diagnosed by allergy skin prick tests or allergy blood tests

Causes

Abnormal immune and nervous system activity

Individuals with AEDS may have abnormal amounts of IgE antibody in their blood. This results from over-activity of some types of immune cells in the body, and under-activity of other cell types. Patients with AEDS are prone to develop a variety of infectious skin diseases caused by viruses, bacteria or fungal infections, and this has led to speculation that a defective immune system may be important in the development of AEDS. There may also be enhanced activity of the patient's nervous system, resulting in an increase in the chemicals that nerves release into the skin, causing the redness and itching.

Food allergy and food intolerance

AEDS may be provoked and worsened by certain foods in food-allergic patients. Approximately 15% of AEDS in children is caused by foods, but less than 5% of AEDS in adults is food-related. A non-allergic reaction to foods or food additives can also provoke AEDS in some cases. A diagnosis of AEDS can be confirmed by reviewing the clinical symptoms in association with the results of allergy skin tests and blood tests, and, if necessary, oral food challenge tests can be performed.

Aeroallergens

Some patients with the IgE-associated variety of AEDS suffer from worsening of their skin symptoms after contact with certain airborne allergens, such as house dust mite, pollens, or animal hairs, and improve after appropriate allergen avoidance strategies are introduced.

Skin barrier and bacteria

Skin is a physical barrier that protects the internal structures and organs of the body, and it is thought that eczema may result from impairment of this barrier function. In AEDS, the skin loses its moisture content and becomes dry and scaly.

Compared to normal skin, there are several differences in the cells in the skin of atopic individuals, even when no eczema is present. A number of friendly bacteria live on human skin, but in individuals with AEDS, a harmful bacterium, Staphylococcus aureus, may grow, infecting the eczematous areas and causing further inflammation. This infection requires treatment with antibiotics. The skin may also be colonized by a yeast, Malassezia.

Psychological factors

The prolonged process of coping with chronic disease, for both the individual with AEDS and the individual's family, can itself be a source of stress, and worsening of eczema has been shown to follow emotionally stressful events. The severity of itching AEDS may be more profound in people who suffer from depression, and increased itching and sweating in eczematous areas of skin can result from an emotional stimulus.

Treatment

Good management of AEDS involves patient education, constant cooperation between the doctor and the patient in the treatment of this chronic disease, and dealing with psychological problems, if any exist. Treatment of symptoms includes frequent use of creams or ointments suitable to the individual's skin type, oil baths, and application of moisturizers. Treatment of inflammation includes topical steroids and antiseptics, wet-wrap dressings in acute cases, and oral antihistamines. If indicated, topical antifungal treatment or antibiotic tablets are also given. In selected cases, new topical non-steroidal immunosuppressant agents can be used. Avoidance of allergens, where appropriate, is important.

Prevention

If a baby's parents, brothers or sisters have atopic, IgE-mediated allergies such as eczema, asthma or hay fever, it is recommended that highly allergenic foods be avoided in the first months of life. This may reduce the likelihood of the baby's immune system coming into contact with allergens before it is fully developed to deal with them. Breast feeding has been shown to protect from, or at least delay, the development of AEDS. If bottle-formulas are used, certain types containing pre-biotics may help to prevent AEDS. If trigger factors have been identified, these should be avoided where possible, and allergen avoidance strategies may be used, such as eliminating specific foods from the diet, encasing bedding against house dust mite allergen and removing pets from the home. The use of creams and emollients is useful to prevent drying of the skin in people predisposed to developing AEDS.

This article is taken from the World Allergy Organisation web site www.worldallergy.org.