Eczema (Atopic dermatitis)

Introduction

• Clinically, the rash often appears identical to that of atopic dermatitis, but the location and history will give you a clue as to the origin – e.g. contact dermatitis may be confined to only the hands.

Epidemiology and Aetiology

• Affects approximately 20-30% of children in developed countries. Incidence is highest in developed countries in urbanised areas
  • Prevalence is increasing
  • Most cases present before the age of 5
• History of atopy (70% of cases)
  • Asthma
  • Hay fever
  • Allergic rhinitis
• Family history – genetic component
• Breast feeding – breast feeding a child as the sole nutrition in the first 3 months of life decreases risk in those with a family history of atopy

Pathology

• Is not fully understood
• It is believed there are two elements to the development of eczema:
  • Reduced barrier effectiveness
    • There is a genetic tendency amongst some individuals to create an ineffective skin barrier. She studies have shown that there is increased permeability of the skin to water in children with eczema. This reduced barrier effectiveness allows normal everyday environmental potential allergens (such as fabrics in clothes, soaps – almost anything that your skin touches!) to permeate the barrier, and reach the deeper skin cells below
    • The barrier layers of the skin is known as the stratum corneum and was previously believed to be made of dead cells and oils and other keratinised tissues. It is now generally believed that it is a living tissue.
    • Filaggrin is an important protein involved in the creation of this barrier. It is thought that many people with eczema have a genetic tendency to produce reduced quantities or poor quality of filaggrin
  • The immune response
    • Once allergens have permeated the barrier, there is an exaggerated immune response to these chemicals. This response is IgE mediated
    • This inflammatory process is sometimes referred to as spongiosis
    • Histologically, it is difficult to differentiate the cause of the spongiosis (i.e. its not usually possible to tell if it is eczema, contact dermatitis or varicose eczema histologically)
• Thinking in terms of the barrier and immune response helps to understand the treatments
  • Emollients help to improve the barrier
  • Steroids help to reduce the inflammation

I explain these barrier and immune response pathologies to my patients. I think it helps people to understand WHY the emollients are so useful – particularly as most patients under dose with emollients. If you can stop the allergens penetrating the barrier – then the inflammation won’t occur. However, once the inflammation is established, its difficult to make it go away without the use of steroids. When patients use both types of topical agents together – I tell them to apply the steroid layer first – otherwise it won’t penetrate the barrier created by the emollients.

• The Hygeine hypothesis is commonly used to explain the increasing incidence of eczema and other atopic disorders. It is believed that in developed countries, increased cleanliness around the home, early childhood vaccination, and small family groups reduced the exposure of young children to pathogens. This results in the over-production/expression of pro-allergic T-cells, increasing the likelyhood of the child becoming atopic.
• In a genetically susceptible individual, there is an IgE-mediated T-cell immune response, after exposure to allergens
• Follows a chronic / relapsing-remitting course

Common Triggers

In a genetically susceptible individual, triggers may include:

• Soaps, detergents, shower gels, bubble baths, washing-up liquids
• Skin infections – particularly staphylococcus aureus
• Extremes of temperature
• Abrasive or synthetic fabrics (e.g. wool, nylon)
• Dietary factors
  • Important in children, less important in adults
  • Most children will “grow out” of skin reactions to food allergens
• Inhaled allergens
  • House dust mites
  • Pollen
  • Pet dander
  • Mould
• Stress
• Hormonal changes in women
  • Pregnancy
  • Flares with different cycles of the menstrual cycle

Clinical features

• Rash, typically on the flexor surfaces (inside of the elbows, wrists and knees), around the eyes, and on the neck. Can also involve the scalp and abdomen.
  • Infants – typically, scalp, face and flexor surfaces
  • Adults – typically chest, neck and flexural
• Pruritus (itch)! – this is the main feature
• Onset is usually within the first 3 months of life, but it can occur later
  • In infants, the rash is typically yon the face, scalp and extensor surfaces
  • The nappy area is usually spared
• Tendency to have generally dry skin throughout life
• A chronic illness with acute flare-ups
• Bacterial infection
  • A common complication
  • Often there is crusting and weeping of the lesions, with surrounding erythema, which may look like cellulitis
• Eczema herpeticum
  • Eczema with co-existing herpes simplex infection
  • Typically very rapid onset
  • Large patches of eczema with concurrent heretic-type blisters
  • Painful
  • May be fevers and lethargy
  • ‘Punched out” lesions of 1-3mm diameter

Diagnosis

• Itchiness in the skin folds in front of elbows and back of knees
• History of asthma or hay fever (one point only even if both are present)
• Generally dry skin
• Visible patches of eczema in the skin folds
• Onset in the first 2 years of life

Investigations

• Not usually required
• Swabs for MC+S may be taken in cases where the rash is not responding to treatment to identify any underlying infection
• Allergy and RAST testing is not indicated – it will only confirm atopy

Differential Diagnosis

• Psoriasis
• Contact Dermatitis
• Seborrheoic dermatitis
• Fungal skin infection
• Lichen simplex chronicus
• Scabies

Prognosis

• Usually improves throughout childhood, and many patients are asymptomatic by age 5.
• Even if there is apparent regression, symptomatic flare-ups still tend to occur throughout childhood and adolescence

Complications

• Widespread herpes infection of eczema lesions
• Typically occurs in children
• Presents with vesicular lesions, typically around the site of a recent dermatitis flare up, although can occur anywhere on the body.
• Patient may become particularly ill, with fever and lymphadenopathy, usually about 5 days after the vesicles appear
• The lesions may later also become infected with staphylococci
• Very rarely, there may be a viraemia, which can be fatal

Cataracts – are a risk in those with long-term disease. Can be a feature of the disease itself, but also result from the use of steroid agents around the eyes, so don’t prescribe steroids for eczema around the eyes!
Eythrodermic eczema – eczema involving >90% of the body!

Management

Removal of identified precipitating factors

• These can be difficult to identify
• Consider changing soaps and shower gels to emollients. Avoid bubble baths.
• Avoid woollen clothes, extremes of temperature
• Dust mite faeces is thought to be a common cause, but is very difficult to control. Some may benefit from measures to control this, such as limiting exposure to carpets, high-filtration vacuuming of mattresses, and use of a Gore-Tex mattress cover
• Avoidance of dietary factors in adults is not thought to be beneficial

Emollients

These help to improve the skins natural barrier, by creating an oily, moisturising layer.

These come in a variety of forms:

• Creams – these are water based, and least potent
• Lotions – these have both water and oil components and are moderately potent
• Ointments – these are oil based and are the most potent
• For example, you might start a patient on e45 cream, and step this up to oil based creams, such as Vaseline (and other petroleum based products – tar is the most potent!), if this is ineffective. Typically, the more potent the emollient, the more greasy the product is (and thus the more unpleasant it is to have it sitting on your skin!)
• Emollients should be used liberally and regularly! – this may mean >500ml/week
• Best applied to wet or moist skin
• Advise to apply every 4 hours, or at least 3-4x per day
• Should be used even when flare-ups are not present in those with dry skin or with recurrent flare-ups
• Using emollients frequently and liberally will reduce the need for steroids
• Special bath/shower emollient products are also available
• Avoidance of soaps if possible. Soaps are very drying to the skin. Wash hands and bathe as little as possible, and use luke-warm water.
  • Some advise the use of emollient as a soap – e.g. patients may be encouraged to apply the emollient as an alternative to washing their hands with soap and water.

Steroids

• Use of steroids – steroid creams are widely used to bring an exacerbation under control.
• Encourage patients to use steroids at the first sign of a flare-up – as it can be more difficult to control once it becomes established
• Note that when they are being prescribed, steroids should be applied before emollients! – otherwise, no steroid gets to the surface of the skin!
• It is recommended to use topical steroids only 1-2x per day.

Steroids are classed according to potency:

• Mild
  • Typically for the face and neck, and for mild flare-ups
• Moderate
  • For more severe flares. Useful for axillae and groin regions
• Potent
  • Same as for moderate
• Very potent
  • NOT for use in children, unless under specialist supervision

Examples:

• Mild corticosteroids – e.g. 1% hydrocortisone, or 0.05% clobetasone (Eumovate – this is more potent than 1% hydrocortisone)
  • On the face – use for <5 days – AVOID AROUND THE EYES – (causes cataracts).
  • On the rest of the body – use for <2 weeks
• Moderate corticosteroids – e.g. betamethasone valerate 0.02%, triamcinolone 0.02%
• Potent corticosteroids – e.g. 0.1% betamethosone valerate, mometasone 1%, methyprednisolone acetylate
• Very potent corticosteroids – e.g. clobetasone propionate 0.05% (Dermovate – highly potent!), betamethasone diproprionate 0.05%
  • NOT FOR USE OF THE FACE
  • On the rest of the body – useful for persistent rash, and in those with lichenification.
• Other preparations – Haelan tape – fludroxycortide – is useful for the fingers, and healing of fissures
• Typical side effects of topical steroids:
  • Side effects are rare with topical agents, so don’t be afraid to use them!
  • Skin thinning
  • Striae formation
  • Telangectasia
  • Adrenal suppression – cushing’s syndrome – rare!

Treatment of staphylococcal infection

• Usually with the use of oral Flucloxacillin 500mg QID for 1-2 weeks
• Topical fusidic acid has fallen out of favour as it is of little proven benefit

Immune modulating agents      

• Pimecrolimus and tacrolimus – are immune modulators (T-cell suppressants) that are licensed for use in moderate to severe eczema. They are usually used as alternatives  or adjuncts to topical steroids, and are available as topic or oral preparations.
• Can cause local stinging / flushing of the skin, but this tends to subside after several days use
• Usually prescribed by a dermatologist

Phototherapy

• May be useful for many patients
• Sunlight is beneficial
• UVA/UVB therapy is effective in treating disease resistant to topical agents. It can cause sun damage, and thus is avoided in children

Systemic therapy

• Very rarely, systemic therapy, such as systemic steroids may be used

Differentiating Psoriasis from eczema

• Can be difficult in children
• The location and nature of plaques adults make differentiation more straightforward
• In children
  • If umbilicus is involved – probably psoriasis
  • Psoriasis plaques tend to be thicker, and often found on the face and scalp
• Treatment is very similar, often with the addition of tar preparations to the emollients, and also utilising vitamin D topical agents

Asteatotic eczema

• “Crazy paving” eczema
• Fissures and cracks on dry skin. Particularly scaly.
• Usually occurs on the shins, typically in elderly patients, but may also be on the trunk.
• Thought to be the result of dehydration of the epidermis
• More common in winter
• Just moisturise and it should go away!

Lip lickers dermatitis

• Soreness around the mouth due to excess lip licking
• Just use emollient e.g. vaseline – moisturises the area, and discourages the habit of lip-licking as it tastes bad

Flashcard

References

• Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
• The biology behind eczema and psoriasis
• Current Understanding in Pathogenesis of Atopic Dermatitis

Read more about our sources

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