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Useful facts on allergy (allergi)

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What is allergy?

The word “allergy” stems from Greek and means altered reaction pattern. Allergy means, therefore, changes in the body’s response to natural substances in the environment which at point of departure are innocuous. These substances are called “allergens” and the most common forms stem from house-dust mites, mould, fur-bearing animals, foodstuffs, medicinal products, metals and pollen grains from grass and trees. 

For allergic individuals a process is initiated involving production of a special antibody (IgE) produced when the allergic individual comes into contact with allergens. This antibody binds to the surface of inflammatory-cells such as mast cells and basophil granulocytes. Such cells are present in the pulmonary mucosa, in the blood and in the skin. In the event of renewed contact with the same allergen, a reaction may arise between the antibody and the allergen. During this reaction, chemical substances are formed which cause problems such as itching, blocked nose, cough and breathing problems. The most important chemical substance formed is histamine. Development of allergy towards a substance can occur rapidly or over a long period.

Who suffers from allergies?

Heredity plays an important role in the development of allergy. If none of the parents is sensitized or allergic, the child has an approximately 15% risk of developing allergy. If just one of the parents is allergic, the risk is approximately 40 %. Where both parents are allergic the risk is approximately 60- 80 %. Children often develop food allergies, but can develop new respiratory allergies into adulthood. Respiratory allergies rarely disappear entirely, but can vary significantly in severity, and the symptoms can improve significantly or disappear almost completely. Some, however, have severe symptoms from both pollen and animals right into adulthood.

What symptoms can allergy cause?

Pollen allergy primarily causes symptoms affecting the eyes and nose, but can also cause symptoms such as headache, lassitude, tiredness and impaired ability to concentrate. Many individuals allergic to pollen will experience discomfort in the mouth and throat when eating raw fruit and vegetables, particularly during the pollen season. This is due to the fact that the substances in pollen are similar to the proteins in food, and allergic cross-reaction results.

In significant allergic reactions, allergic shock, i.e. a sudden and life-threatening drop in blood pressure, can arise. The cause may be an injection (vaccine or radiocontrast medium), insect sting (including wasp stings), drugs or foodstuffs.

For symptoms of contact allergy and food allergy – see separate fact sheet.


More than 40 % of the population will experience one or more instances of allergic reaction in their lifetime. In the majority this will involve mild symptoms. More serious allergy symptoms exist in 10-20 % of the population. The majority develop symptoms of allergy during childhood – even though some individuals only become symptomatic in adulthood.

There is widespread international agreement that the occurrence of allergy has increased over recent decades. There is a strong suggestion that lifestyle factors, such as change in diet and unhealthy internal environments may be of significance. There is also the additional issue of reduced microbial stimulation (the “hygiene hypothesis”) and a change in the composition of bacterial flora in the environment.

Treatment of allergy:

It is recommended that you contact your doctor if you suspect that you have an allergy – even if, in the presence of mild and moderate symptoms, preventive measures are often sufficient. The best measures are to avoid contact, as far as this is possible, with the agent to which you react. In respect of foodstuffs this is difficult- for pollen almost impossible. For many individuals, symptoms of allergy may require drug treatment.

It is important that the correct form of treatment, involving the right drugs, is used. First-line treatment in nasal allergies are so-called “topical” steroids. These are available in spray and powder form. Antihistamines, which are available in tablet form and as eye drops and nasal spray, are also effective forms of medicine, with few and harmless side effects. In the case of lower respiratory tract infections, inhaled drug therapy is the form of intervention most often required. The topical steroids also have a central role here, often in combination with one or more other inhaled preparations. Cortisone spray should, as far as possible, be avoided, but may be indicated prior to special situations (e.g. before exams) or where other treatment options are ineffective.  The effects persist for several weeks.

Allergic shock may occur gradually, or occur acutely and be life-threatening. The few individuals in whom allergy is so severe that they are at risk of allergic shock, should be equipped with adrenaline for injection. The adrenaline should be injected immediately and medical attention sought without delay.

Allergy vaccination

- (See Useful facts on allergy vaccination.)

How is it diagnosed?

If investigations are undertaken whilst the symptoms are acute, e.g. during bouts of hay fever, the findings may be quite typical for allergy. Usually, however, a clinical investigation cannot reveal whether the problem is allergy, hyperactivity, unspecific chemical hypersensitivity or another cause. In such instances special allergy tests, in the form of blood or skin tests (skin-prick test) are required. Antihistamines should not be taken during the seven days preceding the skin-test as they may inhibit the reaction. It is crucial that the doctor ordering the blood tests in the diagnosis of allergy is able to interpret the results. 

No allergy test is 100% reliable. It is completely feasible to have allergy in the absence of a positive allergy test or vice versa. Therefore the medical history is critical in the mapping of allergy. There is no lower or upper age limit for undertaking an allergy test.

How to obtain testing:

Where allergy is suspected the individual should contact their GP. Some general practitioners perform the tests themselves; otherwise one will receive a referral to a specialist, outpatient clinic or hospital. Free Hospital Choice Norway should make it possible to make an informed choice. Relevant information about treatment locations can be obtained via this website and a free telephone number (800 41 004). Free Hospital Choice Norway also provides information about the right to use the hospital of your choice. See www.sykehusvalg.net

Prevention of allergy:

Allergy may be prevented in children who receive breast milk up to the age of 4-6 months. Smoking should be avoided during pregnancy and the child should not be exposed to passive smoking. One should endeavour to achieve the best possible internal climate.