Under the term allergy (from the Greek allos = foreign, ergon = reaction) one understands a reaction of the immune system on the contact with allergens. More than 90% of allergens are harmless to the human body. Nevertheless, the immune system usually reacts violently to the antigens. The symptoms are extremely diverse, depending on the allergen and human individually different: itching, rash, shortness of breath, abdominal pain, vomiting, diarrhea, eczema, hives, hay fever and edema are just a selection of possible symptoms.
Dermatologists check using the so-called prick testson which allergens our body reacts with allergic reactions. To do this, tiny needles filled with tiny amounts of allergens are pricked into the forearm. After ten minutes the doctor checks the skin reactions. If there is redness or wheals, there is an allergy to the corresponding allergen. In this way, allergy sufferers can better avoid the allergens for them substances.
Types of allergies:
Type 1 reaction (immediate type):
The reaction is immediate on contact with the allergen. It comes to the formation of the antibody immunoglobulin E (IgE). Prostaglandins and histamine cause an inflammatory reaction in the respective cells within a few minutes. The type 1 reaction is the fastest and most common immune reaction in allergies.
Type 2 reaction (cytotoxic type):
It leads to the formation of immunoglobulin G (IgG), which binds to antigens that have infested the body's own cells. Through the antigen-antibody reaction, macrophages and natural kill cells recognize the cells and destroy the entire cell via phagocytosis or apoptosis. Difference to type 1: The antigens are circulating freely in the systemic circulation, in type 2, however, the body's own cells have been affected (for example by viruses) or structurally altered (for example by drugs).
Type 3 reaction (immune complex type):
Because of multiple binding sites, the antibodies formed can bind several antigens simultaneously (immune complex), causing them to clump together. Thus, the antigens are indeed ineffective, but can cause inflammation as a foreign body in the entire organism in consequence.
Type 4 reaction (delayed type):
The allergic reaction begins about 24 hours after contact with the allergen. T helper cells cause an inflammatory reaction and stimulate the formation of macrophages by cytokines. The delayed type 4 reaction is characteristic of a contact allergy.
The most common allergies:
pollen allergy (about 40% of the German population)
House dust mite allergy (about 30% of the German population)
Food allergy (about 20% of the German population)
Animal dander (about 15% of the German population)
drug allergy (about 10% of the German population)
Insect venom allergy (about 8% of the German population)
allergy to light (about 3% of the German population)