What happens in my body when I have an allergy?

Basically the same processes occur with an allergy as in a normal immune response. The immune system identifies an intruder as dangerous and throws various mechanisms into gear in order to get rid of the troublemaker. Unlike with a ‘real’ ailment such as a cold, an allergic reaction causes a problem when the body treats harmless substances such as pollen or food ingredients as if they were dangerous and activates its defences. What happens differently in allergy sufferers? And why does the immune system make this mistake?

1
An allergen, such as pollen, comes into contact with the skin or mucosa. Peptides are released. (Charitee-allergie-2-06).

2
These tiny protein chains dock onto IgE antibodies (Charitee-allergie-2-08), that have previously bound to a mast cell. The mast cells are located in places where the body frequently comes into contact with allergens: in the skin, the airways or the gut.

3
Histamine is stored in mast cells (Charitee-allergie-2-07). This is a substance that plays an important role in inflammatory processes. Whenever an allergen binds to the attached IgE antibodies, the mast cell immediately releases the stored histamine and other inflammatory messengers.

4
The released inflammatory substances then cause swelling of the skin, the production of secretions, itching, hives, or a narrowing of the airways.

What exactly is an allergy?

In allergology, allergies are classified into four different types. Type 1 is referred to as immediate hypersensitivity and is a very common type of reaction. It is often equated with the term ‘allergy’. Hay fever, certain food allergies, allergic asthma and insect venom allergies are examples of this type. IgE antibodies play a key role in type 1 reactions. This is a specific class of antibodies that the body makes for its own defence.

In healthy individuals, IgE antibodies are only present in the body in small amounts. Scientists now assume that people with allergies have excess IgE antibodies. The IgE antibodies like to attach themselves to the surface of other cells. One of their preferred landing spots is what is known as a mast cell, which plays an important role in inflammatory processes. Whenever an allergen docks onto an IgE antibody, the mast cell releases messengers that cause inflammatory symptoms.

Illustration: Tobias Borries

Prof. Dr. med. Dr. h.c. T. Zuberbier
Last changes made: July 2016