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Allergies in Germany

A/2006, 15.08.2006

Background information for journalists

An allergy is a heightened, specific immunological defence reaction to substances that is more than the normal one. An allergy is, therefore, a pathological oversensitivity. Sensitisation is the name given to elevated sensitivity to a substance after repeated prior contact. The term sensitisation thus describes allergic diathesis. Pseudoallergy is the name given to oversensitivity which is triggered by mechanisms other than immunological ones. It does, however, involve clinical pictures (symptoms) which correspond or are similar to allergic disorders. A familial predisposition to the development of specific diseases (allergic bronchial asthma, allergic rhinitis, allergic conjunctivitis, atopic dermatitis) is called atopy. It involves immunological oversensitivity of the skin and mucous membranes to natural and synthetic substances. Atopy leads to the increased formation of IgE-type antibodies (of a specific immunoglobulin) and/or a modified non-specific reactivity. Allergic disorders come in many different forms. They include seasonal or year-round rhinitis ("hay fever"), hives, bronchial asthma, the allergic inflammation of the pulmonary alveoli (allergic alveolitis, "farmer’s lung" or "bird raiser’s lung"), contact eczema and atopic dermatitis (neurodermatitis).

An allergic reaction goes through two phases:

  • a sensitisation phase normally without any symptoms and
  • a phase with manifestation of the symptoms.

During the first phase there is initial contact with the allergy-triggering substance (allergen) which leads to an initial immunological response. Renewed contact provokes a second immune response which triggers clinically manifest, adverse reactions with the corresponding symptoms.

Lymphocytes play a major role in the development of allergies. Confrontation with foreign substances and pathogens is part of the normal development process of the immune system. Confrontation with pathogens leads to a reliable and healthy defence and should lead to immunological tolerance. Cow’s milk or chicken protein should not, therefore, trigger any immunological reaction but should be well tolerated. It is assumed that the onset of allergies is due to a disruption of development and maintenance of immunological tolerance.

Gastrointestinal tract

Food allergies occur as intolerances of foods and food additives and are triggered by an allergic (immunological) reaction. By contrast, no allergic-immunological trigger is involved in food intolerances. Occasionally, food intolerances cause symptoms similar to those of food allergies. The term used to describe this condition is a pseudoallergy. Substances which can trigger pseudoallergic food intolerances include additives like sulphites, tatrazine or glutamate. Besides skin and mucous membrane reactions like urticaria, itching, eczema, rhinitis and bronchial asthma, life-threatening immediate reactions (shock) and reactions in the gastrointestinal tract may occur.

The main allergy-causing foods during childhood are cow’s milk and hen’s eggs, fish, soy, wheat and peanuts/nuts. Coupled with a familial predisposition (atopy), a food allergy can lead to neurodermatitis, hay fever and bronchial asthma. Peanuts, fish, hen’s eggs and cow milk are important food allergens for adults, too. However, allergic reactions to hen’s eggs and cow’s milk often disappear in the first years of life. Suffers of pollen allergy have developed allergic reactions to celery, spices, nuts and some types of fruit more frequently in recent years. The observed rise in food allergies can thus be explained by the parallel increase in the number of people who are allergic to pollen. Food allergy sufferers react to certain foods throughout their lives. The food allergy is triggered by contact with the allergy-causing food and the formation of IgE-type antibodies, the immunological reaction. Renewed contact triggers the allergic symptoms. Foods that can cause a pollen-associated allergic reaction have a related structure and a similar protein design (high sequence identity) to the allergic ingredients in pollen. That’s why these foods trigger a food allergy in individuals who are allergic to pollen. In Central Europe 2-3 % of adults and 4 % of infants react allergically to foods. The proportion of the infant group with dermatitis is even as high as 30 %.

More recent studies have shown that substance mixtures, whose individual components do not themselves have any allergenic properties, can encourage the onset of allergies. They can also exacerbate the disorder in allergy sufferers.

Respiratory tract

Allergic reactions can manifest in various parts of the respiratory tract. Allergic rhinitis (allergic cold) is an allergic reaction characterised by short-term discharge from the nose, sneezing and a blocked nose. Frequently, there are other symptoms like inflammations of the maxillary sinuses and inflammation of the ocular mucous membrane. Lengthier, repeated exposure may result in chronic inflammation of the mucous membranes in the nose. The vernacular term for this disorder is “hay fever”. But hay fever can be caused not only by natural allergens like grass and tree pollen but also after contact with chemical substances. Around 12 % of 13-14 year old adolescents and 14 % (Erfurt) and 22 % (Hamburg) respectively of 20 up to 44 year old adults suffer from hay fever. The incidence of hay fever cases has increased in recent years. There are differences between East and West Germany. In the birth cohorts 1942 to 1951 19.8 % (West Germany) and 11.7 % (East Germany) of people had hay fever; in the birth cohorts 1952 to 1961 the figures were 21.5 % (West) and 12.9 % (East). In the birth cohorts 1962 to 1971 the number of hay fever sufferers was as high as 26.8 % (West) and 14.7 % (East).

Allergic asthma is also deemed to be an allergic reaction. It is characterised by an acute narrowing of the respiratory tract and is caused by inflammation of the respiratory tract and a heightened reaction of the bronchia to very different external stimuli (e.g. cold). This condition is described as bronchial hyperreactivity. The reaction to external stimuli is immediate and caused by the release of messenger substances. Delayed reactions are also possible and are triggered by inflammation of the respiratory tract. 2 % (Erfurt) and 4 % (Hamburg) of 20 to 44 year old adults suffer from bronchial asthma. Bronchial hyperreactivity has been diagnosed in 12 % (Erfurt) and 17 % (Hamburg) of 20 to 44 year old adults.

Known foreign substances in the environment, which can trigger a reaction in the respiratory tract, are fragrances. Foreign substances include not only fragrance-containing cosmetics but also fragrances in sprays, incense sticks, scented candles and extracts for vaporisers, used to improve the smell of indoor air. It is assumed that 1-2 % of the population suffers from a fragrance allergy.

Skin

Atopic eczema (neurodermatitis, endogenic eczema, atopic dermatitis) is one of the most common skin disorders. It frequently begins during childhood, often in babies but in theory it can occur at any age. There is a familial predisposition to so-called atopic disorders (hay fever, asthma, eczema). The agonising itching associated with this disorder causes considerable suffering. Particularly during childhood food allergies can encourage the persistence of eczema. Between 6-19 % of children were diagnosed as suffering from atopic eczema by a doctor in an epidemiological study. When eliminating triggers choice of textile plays a special role.

Allergic contact eczema is a non-infectious inflammation of the skin. If there is sensitisation to a substance (a contact allergen), it manifests in the form of eczema when contact with the substance is not completely avoided. Allergic contact eczema is a common problem in Germany. At work contact eczema may prevent people from continuing to do their job fully. Approximately 25 % of all notified occupational diseases affect the skin.

Prevention also plays a major role in this type of allergy. However, it is important to be familiar with the prevalence of sensitisation (positive reaction in the allergy test, eczema is not necessarily visible yet) in the population generally and in various professional sectors in order to obtain timely information about new developments like, for instance, new allergens.

The information network Dermatological Clinics (IVDK, Göttingen) processes data from 40 dermatological clinics in Germany, Austria and Switzerland. At regular intervals it draws up lists of allergens categorised according to incidence. Nickel sensitisations are at the top of the list. They are most frequently caused by wearing fashion jewellery, particularly jewellery for piercings. Other important contact allergenic chemicals are cobalt chloride, potassium dichromate (cement, leather), p-phenylene diamine (colouring agent), thiurames (vulcanisation accelerators), preservatives and formaldehyde. Furthermore, between 1995 and 1998 a major increase in reactions to terpentine oil was recorded, probably through contact with substances which have a similar chemical structure like essential oils and tea tree oil (cross-reactivity).

The Federal Health Survey 2000 recorded a prevalence of allergic contact eczema of 7 %. The incidence of sensitisation without accompanying acute contact eczema is estimated to be between 15 and 20 % by experts.

Smoking and allergies

There are no longer any scientific doubts that passive smoking influences the development of allergic respiratory disorders in children. It also considerably increases the risk of respiratory disorders. The children of parents or mothers who smoke are most at risk. The contributory factors under discussion are the normally close contacts between mother and child and the effects of smoking during pregnancy.

The evaluation of a large number of relevant publications confirms a 30 % higher risk of asthma for children exposed to passive smoking in the home. Repeated studies in the course of their development point to pulmonary function in smoke-exposed children at the lower end of the normal range. The suspicion is that the fine structure of the lungs, particularly during early childhood, is damaged by passive smoking which can lead later to an impairment of their function. Furthermore, studies examined whether children who are constantly exposed to sidestream smoke develop sensitisations more frequently. However, this could not be confirmed up to now. By contrast, another study confirms an association between a mother’s smoking and the development of infantile neurodermatitis.

Prevention

Test methods

Many allergies could be prevented by avoiding any contact with allergenic substances. This applies in particular to contact dermatitis and to sensitisation through foreign substances via the respiratory tract. In order to identify allergens, substances would have to be tested for their allergenic effect before reaching the environment and coming into contact with consumers on a large scale. In this way the access of strong allergens to the market could be prevented. In the opinion of BfR every substance intended for use in consumer products should undergo prior testing for allergenic properties. Test methods for identifying contact allergenic effects are already available. However, it is felt that there is a need for further improvements to the test methods when it comes to potency. No tests are currently available for allergisation (sensitisation) via the respiratory tract. There is a need for more work in this area. This also applies to tests for allergenic effects in the gastrointestinal tract, particularly for novel foods.

Behavioural measures

Irrespective of whether there is a possible genetic predisposition or not, breastfeeding without any administration of complementary food or cow’s milk, at least during the first 4-6 months of life, is an important primary prevention measure when it comes to atopic disorders and food allergies. If babies with a genetic predisposition are not breastfed, then they should be given infant formula with proven reduced allergenicity, again for at least 4-6 months. Dietary measures have proved effective in children with a high genetic (familial) risk. The same applies to proven food allergies: diets in which the allergenic foods are omitted are part of standard treatment. For a few years now efforts have been made to induce a specific oral tolerance along the lines of an active suppression of an immunological (IgE-mediated) reaction by means of slowly increasing the intake (up to 1 year) of the allergenic foods. In order to maintain tolerance, the allergen must be regularly ingested.

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