What are allergies?

  Allergic reactions are messages that the immune system sends to the body. The messages can be almost unnoticeable and appear suddenly, e.g. when you use lotions or eat food you cannot tolerate.

Allergic reactions such as eczema and hay fever are caused by allergens. In order to develop allergies you have to be exposed to one or more allergens for a period of time. It is not possible to develop an allergic reaction to an allergen the first time you come into contact with it. However, if you have been exposed to an allergen over an extended period of time, even short contact with the allergen can provoke an allergic reaction. The most common allergens in Denmark are birch pollen, grass pollen, wormwood, horses, dogs, cats, dust mites, outdoor mould fungus, which most often cause symptoms of the airways, and certain fragrances, which cause contact eczema. If you suspect that you or someone in your family suffers from contact eczema, we recommend that you contact your physician.

WHAT IS AN ALLERGIC REACTION?

Most people use the word allergies 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, also known as 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