Atopic eczema is the commonest type of eczema and the main type that affects children. It usually starts before school age and typically appears first around the age of between three to six months. Atopic eczema usually affects the cheeks and forehead in babies, then the knees when they crawl, and later the hollows or 'flexures' of the arms, wrists, knees and ankles. Most children also have generally dry skin. Atopic eczema may spread on to the torso and cover a large part of the body, as well as the scalp, and the creases around the ears and eyes. It often spares skin covered by nappies in young children. In adults, the hands and face are frequently affected. Atopic eczema is extremely itch.
Atopic eczema can be confused with other forms of eczema or other rashes, and so research studies now use the following criteria for making a diagnosis:
What does 'atopic' mean?
The name 'atopic' is used to describe people with a tendency to contract a group of conditions, namely eczema, asthma and hay fever. Individuals with these conditions are also more likely to have food allergies in early infancy. Atopic conditions often run in families, and children may grow out of one problem and into another as they get older. The usual sequence of conditions is food allergy, followed shortly by eczema in infancy, then later on asthma, then hay fever. This has been called the 'atopic or allergic march'. However, most people do not get all of these complaints and only have one or two atopic conditions in their lifetime.
How common is atopic eczema?
It is widely believed that atopic conditions are becoming more common in developed countries, with increasing numbers of people suffering from atopic eczema, asthma and hay fever over recent decades. Recent studies have estimated that about one in every five children in Europe have atopic eczema, while similar studies from the 1940s showed only one in 20 children to be affected. Although this could be partly because people are now more aware that these conditions exist, there does seem to have been a genuine increase in their prevalence. The reason for this remains a puzzle, but changes in our living environments are implicated. Most children grow out of atopic eczema so it is less common among adults. Estimates of how many adults have atopic eczema range from two to ten per cent.
Although atopic eczema is increasingly common, it should be remembered that most children only get mild eczema and can be looked after by their doctor without the need for hospital based treatment Only a small percentage of children with eczema (1-2 per cent) are severely affected.
Atopic conditions are more common in developed countries than in less developed countries, and are slightly commoner in towns than in the countryside. Atopic eczema is also more widespread in wealthier families and among children who come from small families.
How does atopic eczema affect children?
Atopic eczema can have a big impact on the lives of sufferers and their families. This is being increasingly recognized, and recent studies have looked at the effects of eczema on 'quality of life'. The main areas that affect a child's life are:
Children may also have other atopic problems such as rhinitis (runny nose) and asthma. These sorts of problems can also affect older children and adults.
The usual outcomes of childhood atopic eczema can be simplified as follows:
Are all atopic conditions caused by allergies?
People with atopic conditions have an increased tendency to make an antibody in their blood called 'imunoglobulin E' or 'lgE'. This antibody evolved over millions of years to protect us against gut infections in early life and parasites such as worms. Why people with atopy make larger amounts of IgE antibodies remains unknown. When they are not fighting parasites, IgE antibodies may be misguided and target other substances in our outside world such as food, drugs, animal fur, pollen and house dust mites. These are called allergens. This misdirected immune action can lead to symptoms of allergy.
Allergies appear to play an important role in some of the atopic conditions, for example, hay fever is clearly triggered by pollen allergens. Sufferers get symptoms of sneezing, watering and itchy noses and eyes within minutes of exposure to high levels of pollen, but do not have symptoms during the months of the year when pollen is not present in their surroundings.
Although atopic eczema sufferers may have allergies to various allergens in their environment, the importance of these in making the skin worse is not always clear cut, and eliminating them does not cure the condition. For instance, an eczema sufferer who is allergic to grass pollen may notice that their skin gets red and itchy shortly after sitting on the grass, or flares up the next day. However, avoiding grass does not make the eczema disappear. Similarly, an eczema sufferer who is allergic to cats may notice that the eczema on exposed sites such as the hands and face flares after stroking a cat. Exposure to the cat is thereforean aggravating factor but, once again, avoiding cats does not cure the eczema.
IgE antibodies bind to special cells in the blood, skin, eyelids, nose and airways called 'mast cells'. When these cells come into contact with allergens, a reaction is triggered within minutes and causes the release of a cocktail of chemicals, including a substance called 'histamine'. Histamine causes redness, swelling and itch - just like the rash from a stinging nettle. Antihistamines prevent histamine from working and are useful in reducing the symptoms of these immediate allergy reactions.
Skin prick tests and blood tests can be done to see if someone has IgE-type antibodies to allergens. IgE-type antibodies to common airborne allergens can be demonstrated in 30-40 percent of the general population, but not all will have symptoms of atopic conditions. People who have extra IgE antibodies are said to be 'sensitized' to allergens. However, the situation gets a little confusing here because being sensitized does not necessarily mean that the person will have any symptoms of allergic or atopic complaints.
What causes atopic eczema?
There has been a lot of laboratory research on atopic eczema and this has identified many alterations in the skin. However, the questions of what causes eczema and why it starts as well as why it clears in many children, remain unanswered. It's a bit like someone looking at a cake and identifying some of the ingredients, but not knowing how they were all put together. A similar incomplete understanding applies to many other chronic medical problems. There are two main ways in which atopic eczema skin differs from normal skin.
The various aspects of our environment which may affect atopic eczema will now be considered in more detail.
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