The term eczema covers a range of skin conditions that are itchy and scaly. The name eczema is derived from the Greek word for 'to bubble through'. This is because lesions usually start as vesicles. These are most common in acute eczema but even in the chronic form there is a history of blisters at the start of the condition.
There are three general types. Atopic eczema is 'endogenous' eczema which is triggered by allergy, and may be associated with discoid and pompholyx eczema. Exogenous eczema is triggered by irritants, allergy and sunlight. Unclassified eczema covers a miscellany of other itchy scaly conditions including gravitational eczema.
Although this makes the topic sound complicated, there are general principles for management which make it simpler for the clinician. The most important is that eczemas are usually chronic conditions and so the key to treatment is a clear explanation of the condition to patients. Patients need long-term support with their condition from their GP.
Although acute presentations are uncommon, many patients need frequent reassessment of the best treatment of their condition, and ongoing encouragement to persist with all treatments.
Atopic eczema is common in childhood and starts between four months and two years. Adult onset is also possible but much less common. Most children who have atopic eczema grow out of it, with only about 1-2 per cent of adults affected. Children who develop atopic eczema are more likely to develop asthma and hay fever.
The rash often starts on the face and scalp and develops later on flexures on the knees and elbows. Children have a tendency to scratch and so the rash becomes excoriated. Bacterial infection is a common complication as the defence mechanisms of the skin are compromised.
To treat atopic eczema, in addition to using general measures (see box), antibiotics may be needed for secondary infection and antihistamines to treat itching. Antihistamines are useful in the night-time to prevent scratching during sleep and to aid sleep. The most effective anti-histamines are the ones more likely to cause drowsiness.
Less common treatments are phototherapy, oral cortico-steroids, topical calcineurin inhibitors such as pimecrolimus cream or tacrolimus ointment, ciclosporin and azathioprine.
Aggravating factors are cold weather (which causes dry skin), inconsistent use of treatments and bacterial and herpes simplex infection (which will need to be treated).
Discoid eczema can affect any part of the body, particularly the lower leg. It appears as round or oval pink or brown patches sometimes singly, but often in multiples. Patches are usually itchy. When they settle after weeks or months patients may be left with altered skin colours, sometimes darker and sometimes lighter - postinflammatory hyperpigmentation or hypopigmentation.
Pompholyx eczema affects the hands and feet. Initially there are tiny blisters deep in the skin of the palms, fingers, instep or toes, which are very itchy.
In the mild form the symptoms are minimal but some patients develop blisters and deep painful skin cracks which prevent work. The condition tends to be chronic and as one area heals another starts the cycle of blistering and then cracking. Pompholyx around the nail folds may cause nail dystrophy.
Staphylococcal infection is common. Many also patients have nickel allergy. Some patients are prone to develop it after stress or anxiety.
Treatment follows general principles. Infection and allergy should be considered. A few patients may also benefit from PUVA, methotrexate, dapsone, azathioprine and botulinum toxin (to prevent sweating).
Irritant contact dermatitis
Irritant contact dermatitis is caused by chemicals or physical agents damaging the skin.
Common causes are water, detergents, solvents, adhesives and friction. In infancy napkin dermatitis occurs where there is prolonged contact between skin and urine. Often more than one cause is present.
The skin is initially damaged superficially so that the irritants penetrate more deeply and cause further damage by triggering inflammation.
The initial area of inflammation is where the irritant has been in contact with the skin. Sometimes there is spread to other skin areas, but if this occurs it is more likely that there is allergic contact dermatitis.
Where the cause of the eczema is not obvious patch testing will help in diagnosis. Infection is common and flucloxacillin (or erythromycin) may be needed.
Allergic contact dermatitis
Allergic contact dermatitis may be difficult to distinguish from irritant contact dermatitis, because the rash comes up hours after contact with the substance causing it.
It can spread to areas of skin not in contact with the allergen. It often settles over a few days unless contact reoccurs. It also differs from urticaria, which has an immediate rash with skin contact.
The history of contact is sometimes helpful in diagnosis, for example with nickel allergy occurring after skin contact with nickel in a stud on the waistband of a pair of jeans.
Patch testing is very useful in determining the cause of the skin response so that if it occurs again the agent can be avoided.
Gravitational eczema is an itchy rash found on the legs. It is caused by back pressure on the skin when the veins in the legs do not drain blood back into the body effectively. Other names for it are varicose eczema or stasis eczema.
The most common causes are varicose veins (back pressure due to failure of venous valves from low-pressure to higher-pressure drainage systems) and after a DVT. The rash starts at the bottom of the leg and may be in a patch in front of the inner ankle swelling upwards, or it may be present around the whole shin.
In addition to the usual treatments, additional measures that may help are elevation of legs while sitting so that the ankles are above the level of the hips, graduated compression stockings, and sometimes surgery to the varicose veins if there is ulceration of the skin.
Dr Merriman is a GP in Oxford
General principles for treatment
- Reduction of exposure to trigger factors (where possible).
- Regular emollients (moisturisers) and soap substitutes.
- Intermittent topical steroids.
www.patient.co.uk has four useful patient information leaflets:
- Eczema - atopic.
- Eczema - emollients.
- Eczema - fingertip units for topical steroids.
- Eczema - triggers and irritants.
- Hayes P, McKay T. Churchill's Pocketbook of Medicine. Churchill Livingstone.
- Website containing full list of likely skin allergens: www.dermnetnz.org/dermatitis/contact-allergy.html.