Introduction to allergies - allergy guide

What are allergies?

Allergies are a type of hypersensitivity reaction – conditions where the body's immune system overreacts and causes discomfort, damage, and even death in some instances. The allergic reaction is a response produced within 5 – 10 minutes of encountering an specific allergen – any material that exists in the outside world and provokes an allergic response, but is otherwise not necessarily harmful. Common allergens include pollen, house dust mite faeces, various foods, etc. Atopy is the term given to the genetic predisposition to have allergic reactions.

Allergies are caused by the interaction of the allergen with a chemical known as IgE. This is found on the surface of certain cells in our immune system known as mast cells, although later on other chemicals can also be involved. IgE is produced by plasma cells – another type of cell in the immune system – on the first encounter with the allergen. The allergen, when it comes into contact with IgE on mast cells, causes the mast cell to release other chemical mediators, which cause the symptoms of allergies.

This article deals mainly with the science behind allergies, and will also briefly cover common types of allergy, diagnosis, and treatment. More information about specific types of allergies, diagnostic tests for allergies, and treatment options can be found in their own respective articles.

Allergies Guide Index:

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• What are allergies?
• What's the difference between allergies, intolerance, and sensitivity?
• Overview of the immune system
• How do allergies happen?
• Who gets allergies?

• What are some common symptoms of allergies?
• What are some common allergies?
• How can I check to see what I'm allergic to?
• What treatment options are available?

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Medic8® Family Health Guide : Allergies