Allergies

The following are under discussion as causes for the growing number of allergy patients: e.g. improved hygiene, small family units, and the increased number of irritants (e.g. cigarette smoke, exhaust gases) in all sectors of everyday life and the environment. The triggering of an allergy probably also depends on the allergen itself, its allergenic potency, the concentration and frequency with which it reaches or penetrates into the organism. It is always, however, based on a genetic disposition to develop an allergy, a so-called atopia.

Some frequently encountered allergens of natural origins are e.g. pollen, animal hair, insect venoms, plants or their ingredients. Others are environmental or occupational substances and substances of chemical origins such as metals (primarily nickel), preservatives, fragrances or colorants. The latter, so-called contact allergens, predominantly result in allergic reactions on the skin.

An allergic reaction is triggered by the body's own specific defense (acquired immune system) reacting hypersensitively to normally harmless substances and making itself ill. Independently of the trigger substance, various immunological mechanisms can be activated here. A distinction is made here between four different types of allergies. Allergies of the immediate type (Type 1) and of the delayed type (Type IV) occur most frequently. Further hypersensitivity reactions are cell toxic reactions (Type II) and immune complex reactions (Type III).

Immediate type allergy (Type I)

With the immediate type of allergy, the allergic reaction is normally perceived directly after the absorption of the allergen into the body or after contact with the mucous membranes (eyes, nose). Fifteen to thirty minutes can be assumed to be the most frequent period of time, but in particular with food, e.g. seasoning, or after the intake of prescription drugs, the symptoms can also not appear until after a few hours. Typical allergens or sources of allergens of the immediate type reaction are pollen, animal hair, house dust mites, food and insect venoms. The effects can be relatively slight, e.g. weeping eyes or skin itching (urticaria). Attention should be paid to the reactions that are accompanied by a very strong feeling of warmth and skin tingling, a restriction in circulation or shortness of breath. Emergency first aid is indicated here as the maximum variant, anaphylactic shock, can result in complete circulatory failure with fatal consequences.

The symptoms are attributable to the excessive formation of anti-bodies, the immunoglobulin E (IgE) by the immune system. After contact between the anti-bodies and the allergens (antigen), e.g. in the nasal mucous membranes, complex biochemical processes are set in motion. Among others, histamine and other messenger substances are distributed by so-called mast cells, which then trigger the further inflammation process and depending on the location of the reaction can result in itching and other symptoms. The underlying antigen anti-body reaction can be imagined as a key-lock reaction.

Cell toxic reactions (Type II)

A Type II allergy results in a dissolving of cells, in particular blood cells (reaction of the cell toxic type). The most frequent causes are drugs. The process runs via the formation of IgM and IgG anti-bodies and certain immunological factors (complement). The intolerability of other foreign blood groups also belongs in this category.

Immune complex reactions (Type III)

The Type III allergy is characterised by the formation of immune complexes consisting of antigens and anti-bodies (immunoglobulin IgM and IgG). The cause is contact with a large quantity of antigens, e.g. fungal spores. Activation of immunological factors leads to inflammation and to vascular and tissue damage. Such events are often shown by inflammatory redness on the skin. These can be supplemented by general symptoms such as exhaustion and a temperature. Some examples are farmer's lung or pigeon breeder's lung.

Delayed-type allergy (Type IV))

With the delayed-type allergy, the symptoms usually do not appear until after a day or even later (approx. 24 to 72 hours). That is why they are also called allergies of the delayed type. Skin contact with the allergens (contact allergy) results in an inflammatory reaction, conveyed via T-lymphocytes. The clinical pattern is that of the allergic contact eczema. It is characterised by redness, scaly skin, swelling (oedema), itching, papules, blisters/weeping and/or knots.
Contact allergies can, for example, be triggered by metal ions and products of daily use such as cleaning agents. However, the ingredients of cosmetics, (e.g. preservatives) or plants, clothing and jewellery also trigger allergic skin reactions. The most frequent allergen in the Western world is nickel, as it is frequently a component of such things as buttons and fashion jewellery.

Allergic contact eczemas play a leading role in occupational diseases. In particular, those occupations in which a high percentage of the work is done in a moist environment favour the development of contact eczema. For example, hairdressers, nurses, metal workers and cleaning staff are frequently affected. Investigations suggest that a disrupted skin barrier develops on the basis of the chronically irritated skin that promotes hypersensitivity.