1. Assessing the patient
Atopic diseases (asthma, eczema, allergic rhinitis) are common in western countries, with 40 per cent of the population affected at some point in their lives. Atopic eczema affects 15-20 per cent of UK children and 2-10 per cent of adults, making eczema a significant burden on the NHS.
What causes atopic eczema?
A common misconception is that atopic eczema is an allergy. Definitions of the word allergy range from the scientific (an abnormally excessive immune response to an antigen) to the lay (what can I avoid that will cure my eczema?). Medical and non-medical people stray towards the latter definition, as it suggests patients can control their disease by lifestyle changes.
Atopic eczema is genetically complex. The patient inherits a number of genes that predispose the skin and the cutaneous immune system to interact abnormally. The first gene predisposing to eczema in Caucasians was discovered in 2006. This encodes a protein called filaggrin, which is important in the barrier function of the outer layer of the skin.
While some environmental factors make eczema worse, the basic problem is internally driven. Changing the environment may help a little, but rarely controls eczema adequately.
A methodical history is important when assessing a patient for a potential allergy. If nothing suggestive is found by taking a careful history, it is rarely worth carrying out any testing. Most patients with atopic eczema, urticaria and/or angioedema do not have an allergy. Patients with atopic eczema have an increased incidence of type-1 food allergies, but this is a separate problem from their eczema.
The new patient
Try to allocate 20 minutes to a new eczema case. This can help in getting patients to use treatment correctly and will save time. Ask about fear of steroid creams, dietary exclusions and complementary therapies.
Explain that eczema can be controlled well but not cured, so treatment will need to be continued, and that it often fluctuates for no reason so different levels of treatment will be needed.
The patient needs to know that eczema is likely to be present for some years, but at least 60 per cent of children improve considerably by teenage years, and treatments can be used safely over this period.
2. MAKING A DIAGNOSIS
Two types of allergy testing may be of use: patch tests for type-4 hypersensitivity, and skin prick tests or radioallergosorbent tests (RAST) for type-1 hypersensitivity.
Many so-called allergy tests are of little or no value and are easy to spot because they are not available on the NHS, there are no published validation data, they always show multiple positives (often to dairy products, wheat or gluten and citrus fruits) and are rarely carried out by qualified healthcare professionals.
When to refer for patch tests
Refer patients for patch testing if they have an unusual distribution of eczema (such as ear lobes, periorbital or hands only), if the eczema worsens at work and is better on holiday or with certain hobbies or certain creams, and in resistant otitis externa, venous eczema and pruritus ani.
When to refer for allergy tests
Refer children (and some adults) who develop immediate lip/tongue tingling or swelling (with or without urticaria or anaphylactic symptoms) each time they contact a certain type of food.
Type-1 food allergies are more common in children with eczema, but are not the cause of it. Identifying type-1 allergens and avoiding them will help the urticaria, but not the eczema.
The role of the dietician
Occasionally, especially in infants, eczema may worsen after eating certain types of food, but with no urticarial rash and negative type-1 allergy tests.
This is usually after exposure to dairy products. In such cases, a supervised trial of excluding the food for three months would be justified, often with calcium or iron supplements. If there is no improvement, the food can be slowly reintroduced.
3. Managing the condition
Simple steps can help, including avoiding soaps and using cotton clothing and bedding. Patients should not have pets such as dogs, cats or birds. They should also try to avoid getting too hot. Patients should avoid exposure to smoke.
Triple therapy treatments - emollients, appropriate bathing and topical steroids - should work well in controlling over 95 per cent of patients.
Dry skin gets itchy and emollients, which also have an anti-inflammatory action, counteract this. They should be used liberally and prescribed in 500g tubs, not little tubes. Continuing liberal use lessens the need for steroids.
The patient should use the greasiest emollient tolerated. It may help to use a lighter one by day and a greasier one at night. Avoid prescribing aqueous cream as an emollient to leave on the skin; it can be an irritant in 25 per cent of children with eczema. Show the patient how to apply emollients by gently massaging in the direction of hair growth to prevent folliculitis.
Advise patients to bathe daily with an emollient bath oil; washing off dead skin lessens the risk of infection. A soap substitute, such as aqueous cream, should be massaged into the skin and rinsed off. Advise on a non-slip bath mat.
Weaker steroids can be used long term. Steroids should be used once or twice a day, but not as moisturisers, so make sure patients know which is which.
Explain that very weak steroids are safe to use on the face, and that enough should be used to give the skin a slight glisten. Even scratched and bleeding eczema should be treated: 'don't use on broken skin' means surgical wounds and leg ulcers. Restrict potent steroids to one or two weeks at a time and then tail them off gradually.
Antibiotics and Antihistamines
Only use antibiotics if the eczema is clinically infected, with weeping and crusting.
Sedating antihistamines are useful short term for flare-ups because of their sedating side-effects rather than their antihistaminic properties.
When to refer
Patients who have complied with all the suggested treatments but have experienced no improvement, or who need potent steroids on the body or moderately potent steroids on the face need referral.
Patients who need bandaging also need to be seen in secondary care, as the technique is not an easy one to initiate. The same applies to severe cases needing second-line agents such as phototherapy, oral cyclosporine or azathioprine.
NICE recommends tacrolimus and pimecrolimus only as second-line for atopic eczema not controlled by topical corticosteroids, where there is a serious risk of important adverse effects from further topical steroid use. Pimecrolimus is recommended only for moderate atopic eczema, and only on the face and neck of children age two to 16, and tacrolimus for moderate and severe atopic eczema.
The treatment should only be initiated by experienced physicians after careful discussion with the patient.
National Eczema Week runs from 15-23 September. For more information see www.eczema.org
This article was first published in MIMS Dermatology, September 2007. To register to receive copies see www.hayreg.co.uk/specials.