Atopic eczema
	Allergens and irritants
	Eczema and infection
	Eczema and food
	Eczema and airborne allergy
	Allergen avoidance

Atopic eczema (atopic dermatitis means the same thing) occurs due to an inherited tendency.  This form of eczema usually (although not always) starts in infancy or childhood. Most people with this form of eczema have other kinds of allergy such as food allergy, asthma or hay fever, and most are aware that other family members have a history of allergy. 

The successful treatment of eczema includes not only the use of medical treatments such as steroid creams, ointments and immunosuppressive drugs but also the avoidance of allergens and other eczema triggers. The regular and adequate application of appropriate skin moisturisers is essential for optimum eczema control.

Allergens and irritants

There are believed to be three main reasons why the skin of eczema sufferers is more susceptible to inflammation and damage than normal skin. The substance histamine, present in cells in the skin as part of the normal healthy defence mechanism, is released more easily in eczema sufferers. There is evidence that even the 'healthy' skin of eczema sufferers is well on the way to inflammation, even when it doesn't look as if it is. It also appears that an altered composition of the skin oils may make it less resistant to irritants.

So it comes as no surprise that the skin of eczema sufferers is more than normally sensitive to infection. Exposure to allergens is known to make eczema worse, and this exposure can be to airborne allergens or to food allergens as well as to contact allergens. 

Many substances can act as irritants and these cause eczema to worsen.  Substances encountered at work (and in particular a wide range of chemical compounds) and substances encountered when doing housework (such as detergents that remove the essential skin oils) are particularly important. Intolerance of wool, common amongst sufferers, may be partly based on its irritating effect on the skin, partly related on an allergy to it and partly related to dust mite allergy as woollen clothing is known to contain these. Cigarette smoke may also elicit irritating eczema on the face and around the eyelids.

Eczema and infection

Skin and other infections are known to make eczema worse.  In particular, the common skin microbe Staphylococcus aureus has been studied extensively as an important trigger factor in eczema as it is detected in the skin of more than 90% of all eczema patients.  This bug produces specific toxins and these are detectable in the skin of two thirds of all eczema patients.  These toxins act as potent superantigens, substances capable of stimulating the release of potent inflammatory agents, the very substances that are at the heart of the causation of eczema.  

For this reason, eczema flare-ups that appear to be associated with a build-up of surface skin infection will often respond dramatically to antibiotic creams or ointments, or in some cases five to ten day courses by mouth.  Infection with Staphylococcus should be suspected when patches of eczema become sore, warmer to the touch, and possibly moist or sticky.  Weepy eczema with yellow crusts forming on the surface of the eczema patches are a pretty sure sign that Staphylococcus is present.

In addition to Staphylococcus, the 'dandruff' skin yeast Pityrosporum ovale is now thought to cause a similar problem in a proportion of eczema patients.  Moreover, it appears that Pityrosporum and Staphylococcus have a synergistic effect, the allergic reaction to one increasing the allergic reaction to the other.  Eczema patients most likely to harbour the skin yeast Pityrosporum will have predominantly face, head and neck and upper trunk eczema and are likely to experience intense itching at night.  

Clinical trials have recently shown that antifungal treatment, if necessary combined with antibiotic treatment, can sometimes be effective in such patients.  Interestingly, antifungal drugs that are not absorbed through the gut wall appear to have an effect almost as strong as those that are.  This raises the possibility that sensitivity to gut and food yeasts may be a part of the problem.  As it is known that these yeasts share common allergens, there may be a rational basis to this interesting observation.  It also makes it possible that a change of diet, e.g. through the reduction of yeast- and mould-containing foods, might be helpful in the condition, although no clinical trial of this approach has yet been undertaken.

Eczema and food

Patients with eczema and parents of children with eczema often ask for allergy tests to foods to try to identify if changing the diet will help the eczema.  However this can give a confusing result and this kind of testing should only be undertaken in conjunction with professional guidance.  In particular, allergy tests undertaken through a high-street pharmacy, or, worse still, through a health food shop should not be trusted to give an accurate picture.

Positive skin prick or blood tests to foods are very common amongst patients with atopic eczema, between 60% and 90% will have them, whereas less than 5% of people without eczema will have them.  However these tests only indicate the presence in the blood of specific immune proteins (IgE) to those foods. These proteins can act as antibodies and this would cause a definite allergy to be present, however, it might also mean that an allergy to the food could develop in the future (latent positive).  Paediatrician, Professor Hugh Sampson demonstrated this when he showed that amongst his children patients with eczema, only one-third of positive skin prick test results correlated with positive results from food elimination and challenge.

Children
So if allergy tests give an inaccurate picture, what is the true situation concerning foods and eczema?  Many studies have been done in children that have used elimination diets and 'blinded' challenge tests to identify if particular foods are making eczema worse.  These studies show that between a half and three-quarters of sufferers develop a reaction to one or more foods when tested in this way.  It has also been shown in several studies of children with eczema, that the more severe the condition, the more likely it is that food will be an important trigger.

It can be concluded that in patients with persistent, generalised, moderate or severe eczema, food allergy should always be excluded

Eczema and airborne allergy

Hypersensitivity to the house dust mite is known to be present in about 5% of the population whereas it is found in about 90% of adults suffering from eczema. It is thought that flare-ups of atopic eczema may be caused by dust mites particles that are breathed presumed as well as by skin contact with dust mites. Several clinical studies have reported worthwhile improvements (in some ccases symptom scores have reduced by about a half) of the skin condition after taking very stringent measures to reduce the level of house dust mites.

In addition to mites, sensitisation to animals and pollens may be associated with eczema. Therefore, contact with animals should be avoided for patients with skin or blood test evidence of allergy to animals even when respiratory symptoms do not occur in addition. A small percentage of eczema sufferers will be aware that their condition worsens when they and others are suffering the symptoms of hay fever.

Many studies indicate that the frequency of sensitisation to contact allergens in ingredients of common preparations (e.g., vehicles, preservatives, fragrances, antibiotics, steroids) appear to be higher than normal. Thus, patch testing (sometimes called contact testing - the standard test for contact allergy) should not be neglected in patients with atopic dermatitis because it may reveal important co-factors that are contributing to the maintenance of the eczema in these patients.

Allergen avoidance is the key

by Dr Harry Morrow-Brown

Eczema is very common in infancy, as at least one in five infants are affected. Positive reassurance that it will clear spontaneously by age five is often given, and steroid creams are the main method of treatment. Foods are seldom considered seriously as a cause, yet infancy is the time of life when the diet is at its most simple and easily manipulated, so to eliminate food allergy as a cause of the problem is easiest at this time.

Unfortunately when the eczema eventually subsides, as it does in most cases, it is often replaced by asthma, rhinitis and hay fever. This progress from one sort of allergy to another is known as the allergic march. 

It has been suggested that if the cause is identified and avoided there is some prospect of preventing this response to allergens from becoming a persistent pattern.

When foods cause eczema the reaction is usually slow. It seems that traces of the food are absorbed into the blood without causing a local reaction in the gut, and they then pass into the blood and then the tissue fluids to produce eczema in the sensitised skin.

Allergens such as dust mite or animal danders may access the skin directly through the invisible cracks and defects which are always present in the skin, or the visible cracks from scratching, thus causing eczema to be a sort of constant ongoing skin reaction.

It is often very difficult to help eczema sufferers because there are often not one but several causes. This means that unless they are all eliminated simultaneously the eczema will not improve. Avoiding single foods such as milk will only help if milk is the sole cause, and to exclude one major food in turn risks missing the other foods, and several foods taken together may have additive effects. Inhalants such as dust mites and pets are often involved as well as foods.

© Dr. Harry Morrow-Brown. All Rights Reserved.

Recommended Websites

National Eczema Society
General information from the UK's main eczema charity providing articles and information relating to all aspects of eczema management.
http://www.eczema.org.uk

Asthma, Allergy and Intolerance Information
Whatever your allergy or intolerance, this is a really useful source of information. You can search through articles on allergies, find out about allergy organisations, as well as the latest publications and products available.
http://www.allallergy.net

TalkEczema Website
A very popular UK-based website full of helpful and practical advice about eczema, with contributions from both doctors and patients.
http://www.talkeczema.com