Allergy is the word used to describe a bad reaction that the body has to a particular substance in the environment. Most substances that cause allergies are not harmful and have no effect on people who are not allergic.

Any substance that triggers an allergic reaction is called an allergen. Some of the most common allergens include pollen, house dust mites, mould and pets.

An allergy develops when the body's immune system reacts to an allergen as though it is a threat, and produces antibodies to fight off the allergen, in a reaction called the immune response.

The next time a person comes into contact with the allergen, the body "remembers" the previous exposure and produces more of the antibodies. This causes the release of chemicals in the body that lead to an allergic reaction.

Common allergic disorders include asthma, eczema, hay fever & food allergies.

Symptoms can include sneezing, wheezing, coughing and skin rashes and even anaphylaxis.



Adapted from:

http://www.nhs.uk/conditions/Allergies/Pages/Introduction.aspx