What is an allergic reaction?

The word allergies is often used as an umbrella term for various types of hypersensitivity reactions. You can read more about two types of allergic reactions below. Generally speaking, an allergic reaction occurs when your immune system reacts to an allergen and sends a message to your body, for example in the form of a rash or reddening of your skin.

The first allergic reaction is called “sensitization”. This means that an allergen is encountered and absorbed by cells called macrophages. Macrophages engulf the allergen and send messages to other blood cells (the lymphocytes) to produce IgE-antibodies. The antibodies attach themselves to the mast cells (the allergy cells) found in our mucous membranes, eyes, nose and airways. This way when e.g. pollen comes into contact with the mucous membrane, the antibodies are already ready to capture the allergen. If the allergen is captured by two IgE molecules at the same time, the mast cell releases, among other things, histamine; the mast cell becomes leaky and breaks thereby releasing symptoms of an allergic reaction.

Allergic contact eczema, or type IV allergy, is another type of allergic reaction. Here reactions in the skin are caused by allergens such as fragrances, nickel, chromium, preservatives, plants or gelatins. Symptoms include reddening, itching, bumping or blistering of the skin.

You can find more information at www.hoefeber.astma-allergi.dk