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Allergy Definition

Allergic reactions are based on abnormal regulations within the human immune system.
In case of a so-called immediate allergy (Type I), the following will happen:
If a foreign substance (antigen) penetrates the body,  the immune system develops specific antibodies, or lymphocytes, capable of reacting if the body comes into contact with the foreign substance again.

In the case of immunity, the clash between foreign substances and the substances produced by the body leads to protection, whereas in the case of an allergy, the response is exactly the opposite. Although harmless as such, and tolerated by most people, foreign substances may react with antibodies or sensitised cells, thus causing symptoms of disease. If an allergic person comes into contact with an allergy trigger (allergen), defense cells are mobilised, and the body develops antibodies on a large scale or activates T-lymphocytes. The body is now sensitised, but still shows no symptoms of disease. Only when further contact with the allergen takes place, for example contact with animal skin flakes, the body reacts in a way that the person is aware of the reaction, for example with a runny nose or respiratory problems.

Simply put, you react to a particular substance because your body thinks it is a pathogen and wants to fight it just as it would fight an infection with a flu virus. You suffer from sneezing attacks and a constantly runny nose because a particular type of immune cell (mast cell) releases substances which are highly biologically active, among these especially histamine.

The clinical signs of an immediate allergic reaction - such as itchiness in the nose, a severe runny nose, watery eyes, skin irritation, gastro-intestinal problems or shortness of breath - are a consequence of this release of histamine. How come?

Histamine is only released when the mast cells are aware that you are in contact with a particular substance. Therefore, they must first be sensitised, and this happens through certain antibodies sitting on the skin of the mast cells like spikes on a hedgehog. These "spikes" connect to the invading antigens (foreign bodies), for example pollen,  the mast cells then take notice of the foreign substance and release histamine, and your nose begins to itch, for example.

The allergist distinguishes between different types of allergies:

Type I allergies are the so-called immediate allergies, clinical examples are hay fever, asthma, food allergies and insect venom allergy. The immediate allergies have numerically the greatest importance.

Type II allergy is a very rare form of allergy where, for example, blood cells can be damaged. Possible triggers of a type II allergy are medicines.

Type III allergy represent a frequent form of medication allergy. Antibodies bind to antigens that are carried in the blood, such as drugs. This creates greater concentrations, which may be deposited in the vascular walls of the small vessels, for example on the skin or on the kidneys, causing an inflammatory reaction. This appears on the skin in form of a rash (usually as small red spots) partly with damage to the top layer of skin, as well as with itching.

Type IV allergy is a late reaction allergy. It is the only form of allergy, where the sensitised defense cells (T-lymphocytes) act directly against the allergens. Whereas Type I allergens almost always have to do with protein, Type IV allergens are usually small molecular substances such as metals or chemicals. Clinically expressed, Type IV allergy is known as contact dermatitis.


In childhood years, allergies occur one after another: Atopic dermatitis and food allergies dominate the first years of life, later, the respiratory allergies such as bronchial asthma, allergic rhinitis and hay fever seem to be more common. Allergic reactions to flowers and grass pollens cause hay fever with sneezing attacks, watery eyes and a running or stuffy nose. Similar symptoms may be caused by elements in dust mite feces, but these may cause trouble the year round, and not only during the pollination period. The same applies to a mould allergy. Pollen is said to fly only in spring: But except for two months - November and December -  the pollen calendar holds a number of  unpleasant facts for people with allergies throughout the year. The pollination season starts in January with alder and hazel. In the beginning of February and the entire March, the air is full of  hazel pollen. Birch trees spread their pollen in April and early May, and the dandelion blossoms fly almost throughout the entire spring and summer. And this goes on until November.

If the cause for an allergy remains, it can lead to a broadening of the illness: For example, hay fever can become bronchial asthma. 

Almost every second person will have an Allergy in 2015

Even two generations ago hay fever was an almost exotic disease(!) This poses the question as to the cause of the rapid growth, for which there is empirical evidence. As part of an extensive ISAAC study from 1992 to 1996 in 155 study centres, 463,800 children aged 13 to 14 years were examined. The following figures were calculated for the most commen allergies in Germany:

- Allergic asthma: 5 percent

- Allergic rhinitis (allergic induced rhinitis ): 15 percent

- Sensitisation (against type I allergens): 30 to 40 percent

This study put Germany in the middle. Great Britain, New Zealand and Australia lead the asthma statistics; at the lower end of the scale are countries like Romania and Albania, with  Indonesia at the bottom with an asthma prevalence of under two percent.

Conclusion: The frequency of allergic diseases has been increasing steadily in the last 15 to 20 years, in 2010 every second person will have an allergy says the WHO.

What are the reasons for the increase?

The reasons for these frequent illnesses are not yet fully explored, concrete results can only be expected in the next few years. The following factors are suspected as possible causes:

- Changes in our lives and habits
- Environmental influences, particularly diesel particulates.

A significant risk factor seems to be lifestyle and living style in Western industrial countries, because for example, eastern Germany has experienced a rapid increase in allergic diseases since the fall of the Berlin wall. Within just ten years, the low allergy rate in the East (despite the well-known local pollution!) has increased to the much higher Western level. Even a hereditary component is apparently existent.

Author: edited by Elke Gethmann
Created: 29.7.2004 revised 20.11.2012

Literature / guidelines / EBM:

Weißbuch Allergie in Deutschland 2004, Verlag Medizin und Wissen

The information may under no circumstances be considered a substitute for professional advice or treatment by a doctor. The contents of PureNature should not and may not be used to independently diagnose or begin treatment.