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Monday, 8 April 2013

Atopic dermatitis, what is eczema all about?


Atopic dermatitis or eczema is an inflammatory skin disease which often occurs in the skin creases (backs of knees, elbow creases, armpits, neck and on the face). Atopic dermatitis is characterised by itchy, red, dry and/or cracked skin eruptions. It is a chronic (long-term) condition that is not contagious, but the a tendency to have the condition is genetic .The condition affects males and females equally, affecting 15-20% of school children and 2-3% of adults in the UK as around 65% of cases clear up by age 16. Prevalence of atopic dermatitis symptoms has increased over the last ten years, perhaps due to the increased use of soaps, detergents and frequency of bathing as well as better diagnosis and more awareness.


The symptoms of atopic dermatitis can vary depending on severity of the condition, mild eczema often involves small areas of dry skin that are often itchy. Eczema in the skin creases is said to have a flexural pattern, but other visual symptoms include coin sized areas of inflammation/rash (a discoid pattern) or bumps of inflammation in hair follicles (follicular pattern). Peaks of severity of symptoms are known as flare-ups and skin often becomes very itchy, hot, red and inflamed; because of scratching the skin can bleed or weep and become swollen; skin is also susceptible to staphylococcus aureus infection and impetigo. Repeated scratching can lead to lichenification where the skin is hard and even itchier.


Suffers of atopic dermatitis have a decreased barrier function of the skin, the largest organ of the body, which has the normal role to protect the internal organs of the body from infection and toxins. The loss of this function causes an exacerbation of the Th2 allergic immune response and changes to the lipids (fats) and so the loss of water from the skin tissue. This change is due to abnormal filaggrin expression, filaggrin is a protein which binds to keratin fibres in epidermal (the top layer of skin) cells and encourages the activities of lipid producing enzymes. Filaggrin affects the keratinocytes (skin cells), making them flatten and so affects the amounts of lipid surrounding the cells and how tightly  packed the cells are together (this can also be caused by changes in skin pH (acidity) which is linked to filaggrin expression). This increases the permeability of the skin and increases the number of allergens and pathogens that can penetrate the skin. The inflammation in eczema is due to an allergic response of immune cells, T-lymphocytes (white blood cells). By allowing more allergens into the skin a more severe response occurs and by allowing more pathogens, there is an infection risk and also more immune cells migrate to the skin, so again reactions are severe.  Scratching the skin also attracts neutrophils another type of immune cell which secretes a lipid called leukotriene B4, triggering T-lymphocytes and cause inflammation (blocking the production of this lipid or the immune cell receptors can prevent the development of an eczema reaction in mice).




The loss of the skin barrier function is thought to be due to problems in the gene for Ctip2, which is responsible for controlling synthesis of lipid in the skin and suppresses a protein called TSLP which triggers inflammation, when the gene is faulty, it could lead to skin complaints such as atopic dermatitis.

Th2 cells are a type of T lymphocyte involved in allergic reactions and produces IgE antibodies which cause redness and itching (as well as inhibiting TH1 cells). Scratching damages skin cells opening them up to infection and causing them to secrete chemical messengers encouraging Th2 cells to migrate to the area and cause inflammation. Our immune system develops in the first 6 months of life, and this is when atopic dermatitis symptoms usually manifest, in some people there is an imbalance of Th1 (immunity against infection) and Th2 (immunity against allergens and parasites) cells. People with atopic dermatitis often have Th2 dominance whereas those with TH1 dominance suffer from diseases such as rheumatoid arthritis, MS and Type 1 Diabetes. Due to this TH2 dominance, people with atopic dermatitis are also likely to have asthma, hay fever and allergic rhinitis, however, some people believe that through eczema and so being exposed to allergens that get into the skin is actually what causes sensitivity and lead to these conditions.



Atopic dermatitis flare ups can be caused by many factors. Rough clothing, dry weather, soaps and detergents may irritate the skin; dust, pet hair and pollen may trigger allergic reactions, as might food allergens such as nuts or dairy products. Exercise or hot weather can cause problems due to sweat in the area where eczema is most common. Stress is known to be a trigger of eczema, as are hormonal changes in women, especially in pregnancy (around half of pregnant women who suffer from atopic dermatitis feel their symptoms worsen). Environmental factors such as changes in the seasons and hard/soft water can cause changes to the skin and affect atopic dermatitis.

For people with atopic dermatitis, psychological support may be needed, for people with severe skin irritation, especially in visible areas. In children bullying is a common problem for people with eczema as are self-confidence problems associated with poor self image. In addition, the itchiness of atopic dermatitis can often interfere with sleep which affects concentration and mood; this can have an impact on a child’s school performance, which again can lead to self-confidence issues.

One of the first steps in treating atopic dermatitis is to have a skin test and blood tests, to identify any particular allergies and so plan preventative measures (e.g. I am allergic to grass pollen, so stay inside when grass has been recently mowed). As well as avoiding triggers there are other things that can be done at home, keeping nails short to prevent scratching that can lead to infection, wearing loose fitting clothing of soft fabric, keeping the house free from dust mites and avoiding strong detergents.

Treatment includes emollients which are important in keeping skin moist and can be used liberally all the time (if skin is very dry, should be used every 2/3 hours). Emollients provide a protective film over the skin, this prevents water loss. Emollients are often used after bathing to retain the moisture of the skin. There are many types of emollient, some can be brought over the counter and other prescribed, there are some emollients which can be used a soap substitutes and others to add to bath water. Emollients should be used throughout the year, not only during flare ups, but can over time become ineffective. Emollients should not be shared with other and should have applicators or a pump dispenser in order to minimise infection. During a flare up, emollients should be used very frequently, alongside anti-inflammatory treatment.

When skin is inflamed, topical corticosteroids can be applied directly to the skin; however different strengths may need to be applied to different areas of the body (i.e. milder treatment for the face and strong ointments for flare ups). This treatment should not be used for more than several weeks (a sign that stronger treatment may be needed) and used a maximum of twice daily (applied half an hour after applying emollient to the affected area). Corticosteroids are measured in fingertip units (see below) which, as they must be spread thinly, can cover a large area of skin. When applied, they can often sting or burn and are not suitable for long term treatment as can have side effects such as thinning of the skin (especially around creases), acne, increased visibility of blood vessels (in particular the cheeks) and increased hair growth on the skin.

Other treatments include antihistamines which can reduce the itching associated with atopic dermatitis as they prevent the release of histamine which triggers allergic responses when in contact with allergens, some antihistamines are sedating and cause drowsiness, these are for short term use only and people should not drive or operate heavy machinery when on this treatment. Similarly topical immunosuppressants reduce the immune response to a particular area. For severe flare-ups, oral corticosteroids can be prescribed to reduce inflammation (these also are used to treat asthma). The course of treatment is about two weeks long, one tablet a day. This medication can have severe side effects if used for an extended period of time, such as hypertension (high blood pressure), osteoporosis (easily broken bones), fluid retention (and so swollen ankles/legs) and in children can affect their growth. To prevent scratching and allow the skin to heal, medicated dressings (which also prevent itchiness) are used but only on uninfected skin. If the skin becomes infected usually antibiotic treatment is prescribed, this is usually tablets, but could involve antibiotic creams applied to the infected area. If infected with herpes simplex virus (which causes cold sores) antiviral treatment will be given. In the long term, people prone to infection use antiseptic creams, as antibiotic treatment could lead to resistance. Dermatologists could also offer phototherapy which involves ultraviolet light to treat the affected area.

There is currently no cure for eczema, however new studies into the genetics behind skin problems could lead to epigenetic cures in the future and there are many treatments that can alleviate or control the symptoms. In the majority of cases, children ‘grow out’ of eczema and their symptoms subside naturally in their teenage years.

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