In the next in our series exploring some common misconceptions about conditions seen in general practice, GP dermatology specialist Dr Stephen Hayes dispels some myths about eczema – and explains some facts you may not know…
Myths
Myth 1. Topical steroids are dangerous
The introduction of topical steroid creams and ointments in the 1960s revolutionised the management of inflammatory skin disease. But, as with most potent drugs, there are risks. They were over prescribed in the 1970s: as a student back then I saw patients with steroid rosacea due to inappropriate use of potent steroids on the face, and skin thinning and striae especially of the ante-cubital fossa where the skin is thinner.
Doctors soon got wise to these side effects and acted accordingly. However, bad news sticks around, and some people still fear topical steroids, especially for children, and may refuse them, citing fears of systemic effects like adrenal suppression, osteoporosis or diabetes. Such steroid phobia may now be a bigger problem than steroid side effects.
Most dermatologists today advise starting with a strong steroid and reducing potency or frequency of application at review. When I have seen harms from topical steroid use, it has usually been due to potent steroid on the face, or an unwise long term repeat prescription without emollient or face-to-face review. More often, I see patients suffering needlessly due to phobia-driven steroid refusal.
Myth 2. Eczema is often due to contact or food allergy, which requires testing
Allergic contact allergy is usually suspected on the history, timing and distribution of the rash, but in most cases of eczema, allergy is irrelevant and it’s a waste of time and resources looking for it. Patch testing involves a fridge full of costly chemicals and typically involves three trips to outpatients in a week, so it’s a secondary care investigation which is only appropriate for select cases.
Food allergy and eczema may co-exist, but (with the exception of severe atopic eczema in infants under one year of age, where CMPA may be a direct cause) it now seems that eczema causes food allergy through allergens penetrating leaky skin.
Myth 3. Eczema is due to anxiety
Like so many myths, there is some truth to this. A chronic itch-scratch cycle related to anxiety or depression may lead to a localised rash in some individuals. Lichen simplex is a circumscribed red scaly rash most often found by the elbow, flank, shin or behind the ear – places where a nervous hand finds somewhere to scratch. ‘Picker’s nodule’ is similarly caused by chronic picking or biting, most often on the hands. But neither of these problems is true eczema.
The reality is that if someone experiences both eczema and anxiety, the eczema is more likely to be a cause rather than a result of anxiety. There is growing interest in psychodermatology and some evidence of inflammatory skin disease causing mental health issues via the skin/brain axis. A recent research paper found that a high proportion of children and young people with skin conditions had been bullied because of their rash, often leading to mental health issues. It is more likely that skin problems cause mental health problems than the other way around.
Myth 4. It is very difficult to diagnose eczema in skin of colour
Until recently most dermatology research and textbooks were based on white patients, because most dermatology research and publication was done in Europe and the USA. Dermatology organisations like the Primary Care Dermatology Society, British Association of Dermatologists and European Academy of Dermatology and Venereology are all now working to address the historical racial imbalance in dermatology research and guidance.
Many skin conditions present differently according to the patient’s skin type. Eczema looks different in black skin, because the erythema is concealed by melanin. However, everything else is the same – the history, itch, excoriations, lichenification and vesicles (which need to be looked for with a lens and a light). It’s just the erythema that is absent.
Myth 5. Antihistamines are helpful for eczema
Old fashioned sedating antihistamines like promethazine can help, and (rightly or wrongly) have probably helped many anxious parents get through the night by helping their scratchy kids off to sleep. But histamine isn’t really the problem with eczema, so there is no logical reason why non-sedating antihistamines should help, good as they are for hay fever and urticaria. A Cochrane review found there was no trial based evidence of either benefit or safety. That said, some patients say they find them helpful, whether it’s a placebo effect or not, so a therapeutic trial for a week or two is arguably excusable give that these are very safe medicines.
Most cases of mild to moderate eczema can (and should) be managed in Primary Care by what I call the ‘ABC’ approach:
- Avoid anything that aggravates
- Bland emollients, buckets full
- Corticosteroid (with care and caution)
Severe and recalcitrant cases deserve to see a dermatologist, where more advanced therapeutic options are available.
Facts
Fact 1. Atopic eczema is mainly a disease of skin barrier function
Atopic eczema has long been known to have a large hereditary component, but now we know why. It is largely due to a failure of skin barrier function caused by mutations affecting the protein filaggrin. Filaggrin sticks skin cells together to make a functional barrier. When it malfunctions, the skin becomes leaky – allowing toxins, pathogens and allergens to penetrate and cause inflammation. This is why emollients (the stickier the better) are useful to restore skin barrier function. It’s important to be aware that any detergent (ie, soap, shampoo, washing up liquid) can worsen eczema by degreasing the skin.
Fact 2. Eczema is not one, but several conditions
Atopic eczema is the most typical form of the disease, but there are other variants.
Contact allergic dermatitis is a type 4 delayed hypersensitivity reaction due to the individual’s immune system reacting to a chemical that most people are OK with. Allergens include nickel, acrylates (including nail varnish), some plants, chemical preservatives, topical antibiotics and various other allergens. The history is vital to the diagnosis, which can be confirmed if necessary by patch testing, involving a battery of appropriate substances applied to the skin and reviewing the reactions.
Contact irritant dermatitis is also caused by chemical contact but is a direct reaction to abrasive or caustic substances such as acids or alkalis rather than an allergy.
Discoid eczema tends to affect middle aged or older patients and consists of discrete well-defined patches and plaques of intense inflammation. Staphylococcus aureus may be involved, and antibiotics may be needed as well as very potent steroids. We don’t know the cause.
Asteatotic eczema is common in old age where the skin is naturally drier and thinner and is exacerbated by excessive use of soap and other detergents which dry out the skin. It can be tricky trying persuading people they need to bathe or shower less often: my strategy is to explain that detergents solubilise oil in water, which is necessary to keep ourselves clean but if overdone can dry out the skin’s necessary oils and affect skin barrier function leading to dry, cracked and eventually inflamed skin. Emollient based soap substitutes, or water miscible emollients applied after bathing while the skin is still moist can help.
Fact 3. The prognosis for most cases of infant eczema is good
Although it’s horrible to have a baby crying with eczema, the outlook is quite positive. The condition can be expected to clear in about 65% of children by age 7 and about 74% by 16. There may be flares, and increased risk of allergic dermatitis developing due to the underlying filaggrin/skin barrier deficiency, but parents can be reassured that children are likely to improve, especially if regular emollient therapy is used and flares treated with topical steroid as indicated.
Fact 4. Emollients are often prescribed in inadequate quantities
As explained above, emollients are vital to repair deficient skin barrier function, but only if they are used. It takes at least 30 g to cover an adult skin, so if used only twice a day, that’s 420 g a week. Do the math, prescribe enough, and don’t expect the patient to buy their own just because these are over-the-counter medications. Eczema is as much an organic disease as hypertension or diabetes.
Fact 5. Eczema can become secondarily infected
Our wonderful skin, amongst other attributes, protects us from pathogens and other external assaults. However, the epidermis can be broken in eczema due to scratching, creating portals of entry. Staph aureus and herpes simplex are two of the organisms that may take the opportunity to set up a secondary infection. Staph in particular can exacerbate eczema due to production of exotoxins which act as superantigens (think of toxic shock syndrome and staphylococcal food poisoning).
Watch out for unexplained exacerbations, yellow exudate, pustules and fever. Oral antibiotics may be necessary. There is a useful article by the National Eczema Association. Also watch out for eczema herpeticum which requires oral antivirals.
Dr Stephen Hayes is a retired GPwSI, Associate Specialist in Dermatology at the University of Southampton and Executive board member, International Dermoscopy Society
